35-1-3.pdf

TO 35-1-3

TECHNICAL MANUAL

CORROSION PREVENTION AND CONTROL, CLEANING,

PAINTING, AND MARKING OF USAF SUPPORT

EQUIPMENT (SE)

This manual supersedes TO 35-1-3 dated 1 September 2006, Change 10 dated 5 August 2013.

DISTRIBUTION STATEMENT A - Approved for public release; distribution is unlimited. PA Case Number 05-07173. Other requests for this document shall be referred to 406 SCMS/GUEE, Robins AFB, GA 31098. Questions concerning technical content shall be referred to AFRL/

RXSSR.

Published Under Authority of the Secretary of the Air Force

26 APRIL 2014

Dates of issue for original and changed pages are:

Original. . . . . . . .0. . . . . . .26 April 2014

TOTAL NUMBER OF PAGES IN THIS PUBLICATION IS 202, CONSISTING OF THE FOLLOWING:

Page *Change No. No.

Page *Change No. No.

Page *Change No. No.

Title A i - ix x Blank xi - xii 1-1 - 1-15 1-16 Blank 2-1 - 2-17 2-18 Blank 3-1 - 3-25 3-26 Blank 4-1 - 4-108 5-1 - 5-5 5-6 Blank 6-1 - 6-3 6-4 Blank 7-1 - 7-4 A-1 - A-6

TO 35-1-3

LIST OF EFFECTIVE PAGES

INSERT LATEST CHANGED PAGES. DESTROY SUPERSEDED PAGES.

NOTE The portion of the text affected by the changes is indicated by a vertical line in the outer margins of the page. Changes to illustrations are indicated by shaded or screened areas, or by miniature pointing hands.

* Zero in this column indicates an original page.

A USAF

TABLE OF CONTENTS

Chapter Page

LIST OF ILLUSTRATIONS . . . . . . . . . . . . . v

LIST OF TABLES . . . . . . . . . . . . . . . . . . . . vi

FOREWORD . . . . . . . . . . . . . . . . . . . . . . . vii

SAFETY SUMMARY . . . . . . . . . . . . . . . . . xi

1 CORROSION THEORY, IDENTIFICATION,

CAUSES AND EFFECTS . . . . . . . . . . . . 1-1

1.1 PURPOSE. . . . . . . . . . . . . . . . . . 1-1

1.2 DEFINITION OF

CORROSION . . . . . . . . . . . . . 1-1

1.3 CHEMICAL DEFINITIONS . . . . . 1-1

1.3.1 Atom . . . . . . . . . . . . . . . . . . . . . 1-1

1.3.2 Electron . . . . . . . . . . . . . . . . . . . 1-1

1.3.3 Ions . . . . . . . . . . . . . . . . . . . . . . 1-1

1.3.4 Electrolyte. . . . . . . . . . . . . . . . . . 1-1

1.4 THEORY OF CORROSION . . . . . 1-1

1.4.1 Anode . . . . . . . . . . . . . . . . . . . . 1-1

1.4.2 Cathode . . . . . . . . . . . . . . . . . . . 1-1

1.4.3 Electrolyte. . . . . . . . . . . . . . . . . . 1-1

1.4.4 Electrical Path . . . . . . . . . . . . . . . 1-1

1.5 DEVELOPMENT OF

CORROSION . . . . . . . . . . . . . 1-2

1.5.1 Corrosion Origination

Locations . . . . . . . . . . . . . . . . 1-2

1.5.2 Corrosion Under Painted

Surfaces . . . . . . . . . . . . . . . . . 1-2

1.6 FACTORS INFLUENCING

CORROSION . . . . . . . . . . . . . 1-4

1.6.1 Type of Metal . . . . . . . . . . . . . . . 1-4

1.6.2 Dissimilar Metal Coupling (Galvanic

Corrosion). . . . . . . . . . . . . . . . 1-4

1.6.3 Anode and Cathode Surface

Area. . . . . . . . . . . . . . . . . . . . 1-4

1.6.4 Climate. . . . . . . . . . . . . . . . . . . . 1-4

1.6.4.1 Desert . . . . . . . . . . . . . . . . . . . . 1-4

1.6.4.2 Temperate Zones . . . . . . . . . . . . . 1-4

1.6.4.3 Tropics . . . . . . . . . . . . . . . . . . . . 1-4

1.6.5 Heat Treatment and Grain

Direction. . . . . . . . . . . . . . . . . 1-5

1.6.6 Electrolytes . . . . . . . . . . . . . . . . . 1-5

1.6.7 Microbial Induced/Influenced

Corrosion . . . . . . . . . . . . . . . . 1-7

1.6.8 Mechanical Stress. . . . . . . . . . . . . 1-7

1.6.9 Time . . . . . . . . . . . . . . . . . . . . . 1-7

1.6.10 Manufacturing . . . . . . . . . . . . . . . 1-7

1.6.11 Storage . . . . . . . . . . . . . . . . . . . . 1-7

1.6.12 Degradation of Non-metals . . . . . . 1-8

1.6.13 Preventive Maintenance (PM) . . . . 1-8

1.7 TYPES OF CORROSION . . . . . . . 1-8

Chapter Page

1.7.1 Uniform Etch Corrosion . . . . . . . . 1-9

1.7.2 Galvanic Corrosion. . . . . . . . . . . . 1-9

1.7.3 Pitting Corrosion . . . . . . . . . . . . . 1-10

1.7.4 Intergranular Corrosion . . . . . . . . . 1-10

1.7.5 Exfoliation Corrosion . . . . . . . . . . 1-11

1.7.6 Concentration/Crevice

Corrosion . . . . . . . . . . . . . . . . 1-11

1.7.7 Stress Corrosion Cracking . . . . . . . 1-12

1.7.8 Hydrogen Embrittlement . . . . . . . . 1-12

1.7.9 Corrosion Fatigue. . . . . . . . . . . . . 1-12

1.7.10 Filiform Corrosion . . . . . . . . . . . . 1-13

1.7.11 Fretting Corrosion . . . . . . . . . . . . 1-14

1.8 METALS AFFECTED BY

CORROSION . . . . . . . . . . . . . 1-14

1.8.1 Magnesium . . . . . . . . . . . . . . . . . 1-14

1.8.2 Steel. . . . . . . . . . . . . . . . . . . . . . 1-14

1.8.3 Aluminum. . . . . . . . . . . . . . . . . . 1-14

1.8.4 Copper and Copper Alloys. . . . . . . 1-14

1.8.5 Stainless Steel . . . . . . . . . . . . . . . 1-15

1.8.6 Nickel and Chromium. . . . . . . . . . 1-15

2 CLEANING . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1 GENERAL . . . . . . . . . . . . . . . . . 2-1

2.1.1 Introduction. . . . . . . . . . . . . . . . . 2-1

2.1.2 Support Equipment (SE) Wash

Cycles . . . . . . . . . . . . . . . . . . 2-1

2.1.3 Definition of Cleaning. . . . . . . . . . 2-1

2.1.4 Types of Cleaners. . . . . . . . . . . . . 2-1

2.1.5 Methods of Cleaning . . . . . . . . . . 2-1

2.1.6 Cleaning Materials . . . . . . . . . . . . 2-6

2.1.7 General Cleaning Material and

Processes . . . . . . . . . . . . . . . . 2-11

2.1.7.1 Cleaning Solutions . . . . . . . . . . . . 2-11

2.1.7.2 Cleaning Compounds . . . . . . . . . . 2-12

2.1.7.3 Water Temperature . . . . . . . . . . . . 2-12

2.1.7.4 Deployed/Remote Sites . . . . . . . . . 2-12

2.1.8 Cleaning of Non-metal Parts Prior to

Painting . . . . . . . . . . . . . . . . . 2-12

2.1.8.1 Composites . . . . . . . . . . . . . . . . . 2-12

2.1.8.2 Plastics . . . . . . . . . . . . . . . . . . . . 2-12

2.1.9 Cleaning of Electrical Parts . . . . . . 2-12

2.1.10 Preparation of SE for Cleaning. . . . 2-13

2.1.11 Cleaning of Engine Components and

Enclosures. . . . . . . . . . . . . . . . 2-13

2.2 MECHANICAL CLEANING. . . . . 2-14

2.2.1 General Information . . . . . . . . . . . 2-14

2.2.2 Coating Removal on Composite

Surfaces . . . . . . . . . . . . . . . . . 2-14

2.2.3 Coating Removal on Metallic

Surfaces . . . . . . . . . . . . . . . . . 2-15

2.2.4 Grinding . . . . . . . . . . . . . . . . . . . 2-15

2.2.5 Wire Brushing . . . . . . . . . . . . . . . 2-15

i

2.2.6 High-Pressure Water (HPW) Paint

Removal Method . . . . . . . . . . . 2-15

2.2.6.1 Authorized HPW Equipment . . . . . 2-15

2.2.6.2 Training Requirements . . . . . . . . . 2-16

2.2.6.3 Personnel and Equipment Prepara-

tion Prior to HPW . . . . . . . . . . 2-16

2.2.6.4 HPW Paint Removal Operation . . . 2-16

2.2.6.5 Post HPW Paint Removal

Cleaning . . . . . . . . . . . . . . . . . 2-16

3 PAINTING, SEALING, CORROSION PRE-

VENTIVE COMPOUND

APPLICATION . . . . . . . . . . . . . . . . . . . 3-1

3.1 GENERAL . . . . . . . . . . . . . . . . . 3-1

3.2 DEFINITION OF EXPOSURE. . . . 3-1

3.3 REQUIREMENTS FOR PAINTING

- FIELD LEVEL . . . . . . . . . . . 3-1

3.3.1 Corrosion Control Scoring Program

and Complete Repainting Criteria . . . . . . . . . . . . . . . . . . 3-1

3.3.1.1 Corrosion Scoring . . . . . . . . . . . . 3-1

3.3.1.2 Scoring Categories . . . . . . . . . . . . 3-1

3.3.2 Abrasive Blasting . . . . . . . . . . . . . 3-2

3.3.2.2 Medium Pressure Water

Blasting . . . . . . . . . . . . . . . . . 3-2

3.3.2.3 Scuff Sand and Overcoat . . . . . . . . 3-2

3.3.3 Temporary Coating Repairs . . . . . . 3-3

3.3.3.1 Rust Converters . . . . . . . . . . . . . . 3-3

3.3.4 Touch-up Primer . . . . . . . . . . . . . 3-3

3.4 REQUIREMENTS FOR PAINTING

- DEPOT LEVEL AND CON-

TRACTOR SUPPORT . . . . . . . 3-3

3.4.1 Corrosion Rework

Determination . . . . . . . . . . . . . 3-3

3.4.2 Contractor Compliance . . . . . . . . . 3-4

3.5 AUTHORIZED COLORS, SEM-

PENS, AND MATERIALS . . . . 3-4

3.5.1 SE Standardized Colors. . . . . . . . . 3-4

3.5.2 SE Standard Topcoat. . . . . . . . . . . 3-4

3.5.3 Authorized Colors for Liquid Oxy-

gen, Nitrogen, Storage Carts and Tanks . . . . . . . . . . . . . . . . . . . 3-4

3.5.4 Passenger or Loading Ramps . . . . . 3-5

3.5.5 Presidential Support Equipment and

USAF Demo Team . . . . . . . . . . 3-5

3.6 CORROSION TREATMENT FOR

STEEL CABLES . . . . . . . . . . . 3-10

3.7 PIANO TYPE HINGES . . . . . . . . 3-10

3.8 MATING SURFACES PROTEC-

TION REQUIREMENTS . . . . . 3-11

3.8.1 Mating Surfaces - Bare Steel . . . . . 3-11

3.8.1.1 Mating Surfaces - All Other

Metals . . . . . . . . . . . . . . . . . . 3-11

3.8.2 Sealers and Sealant Usage . . . . . . . 3-11

Chapter Page

3.9 ACOUSTICAL MATERIAL

PRECAUTIONS . . . . . . . . . . . 3-12

3.9.1 Coustifoam PUI and AF . . . . . . . . 3-12

3.9.2 Nonmetallic Fasteners . . . . . . . . . . 3-13

3.10 DRAINAGE . . . . . . . . . . . . . . . . 3-13

3.10.1 Fluid Collection Points . . . . . . . . . 3-13

3.10.2 Modifying Fluid Collection

Points . . . . . . . . . . . . . . . . . . . 3-13

3.11 MAINTENANCE STAND RAILS

AND RAIL HOLDERS. . . . . . . 3-13

3.11.1 Drain Holes. . . . . . . . . . . . . . . . . 3-13

3.11.2 Drain Hole Corrosion Prevention

and Treatment . . . . . . . . . . . . . 3-13

3.12 HOLLOW STRUCTURAL

MEMBERS. . . . . . . . . . . . . . . 3-14

3.12.1 Drainage for Closed Hollow Mem-

bers, When Open Drain Holes are Possible . . . . . . . . . . . . . . . . . 3-14

3.12.2 Drainage for Closed Hollow Mem-

bers, When Open Drain Holes are Not Possible . . . . . . . . . . . . . . 3-14

3.13 CORROSION PREVENTIVE

COMPOUNDS (CPC). . . . . . . . 3-14

3.13.1 MIL-PRF-81309. . . . . . . . . . . . . . 3-15

3.13.2 MIL-DTL-85054 . . . . . . . . . . . . . 3-15

3.13.3 MIL-PRF-16173 CPC Solvent Cut-

back, Cold Application . . . . . . . 3-15

3.13.4 MIL-PRF-63460 Lubricant, Cleaner, and Preservative for Weapons and Weapon Systems . . . . . . . . . . . 3-15

3.13.5 MIL-L-87177 Lubricants, Water

Displacing. . . . . . . . . . . . . . . . 3-15

3.13.6 CPC Methods of Application . . . . . 3-16

3.14 CPC APPLICATION ON FER-

ROUS ALLOYS . . . . . . . . . . . 3-16

3.15 CPC APPLICATION ON OTHER

ALLOYS . . . . . . . . . . . . . . . . 3-16

3.16 COATING APPLICATIONS . . . . . 3-18

3.16.1 Material Selection . . . . . . . . . . . . 3-18

3.16.2 SE Surface Preparation

Categories . . . . . . . . . . . . . . . . 3-18

3.16.3 Organic Zinc-Rich Primer . . . . . . . 3-18

3.16.4 MIL-PRF-85285 Polyurethane, Type

I . . . . . . . . . . . . . . . . . . . . . . 3-19

3.16.5 Thermal Spray Coating

Systems . . . . . . . . . . . . . . . . . 3-19

3.17 FIELD LEVEL MAINTENANCE

PAINTING

REQUIREMENTS . . . . . . . . . . 3-21

3.17.1 Touch-Up Painting . . . . . . . . . . . . 3-21

3.18 MAINTENANCE PAINTING . . . . 3-21

3.18.1 Maintenance Painting

Restrictions . . . . . . . . . . . . . . . 3-21

3.18.2 Prepackaged Coating Touch-Up

Kits . . . . . . . . . . . . . . . . . . . . 3-22

TO 35-1-3

TABLE OF CONTENTS - CONTINUED

ii

3.18.3 Radiators Coatings . . . . . . . . . . . . 3-22

3.19 LIQUID OXYGEN AND LIQUID

NITROGEN SERVICING

CARTS AND STORAGE

TANKS . . . . . . . . . . . . . . . . . 3-22

3.19.1 Authorized Materials for Liquid

Oxygen and Nitrogen Tanks. . . . 3-22

3.20 WALKWAYS AND STEPPING

SURFACE COATINGS. . . . . . . 3-22

3.21 COLORS FOR WASTE

CONTAINERS . . . . . . . . . . . . 3-22

3.22 SE UNDERCOATING . . . . . . . . . 3-23

3.22.1 SE Undercoating

Considerations . . . . . . . . . . . . . 3-23

3.23 STORAGE COMPARTMENTS . . . 3-23

3.24 SPLIT WHEEL ASSEMBLIES . . . 3-23

3.24.1 Split Wheel Coating

Requirements. . . . . . . . . . . . . . 3-23

3.25 MUFFLERS . . . . . . . . . . . . . . . . 3-23

3.26 MISCELLANEOUS CLEANING,

SEALING, AND CPC

REQUIREMENTS . . . . . . . . . . 3-24

3.26.1 Sealing of Addressograph or Dash-A

Plates . . . . . . . . . . . . . . . . . . . 3-24

3.26.2 Electrical Hardware and

Terminals . . . . . . . . . . . . . . . . 3-24

3.26.3 Light Assemblies . . . . . . . . . . . . . 3-24

3.26.4 Internal Electrical Components: Cir-

cuit Breakers, Relays, etc . . . . . 3-24

3.26.5 Electrical Connectors . . . . . . . . . . 3-25

3.26.6 Switches . . . . . . . . . . . . . . . . . . . 3-25

3.26.7 Wire Harness and Cables. . . . . . . . 3-25

3.26.8 Heli-Coil Insert Replacement . . . . . 3-25

4 MARKING OF SUPPORT EQUIPMENT . . . 4-1

4.1 GENERAL . . . . . . . . . . . . . . . . . 4-1

4.1.1 Marking Illustrations and

Legends . . . . . . . . . . . . . . . . . 4-1

4.2 SAFETY AND SERVICING

MARKINGS . . . . . . . . . . . . . . 4-1

4.2.1 National Star Symbol . . . . . . . . . . 4-1

4.2.2 Marking Requirements . . . . . . . . . 4-1

4.2.3 Product Identification . . . . . . . . . . 4-2

4.2.4 SE Reflectorization . . . . . . . . . . . . 4-2

4.3 AGENCY IDENTIFICATION

MARKINGS . . . . . . . . . . . . . . 4-2

4.3.1 Air Force Owned - Contractor Oper-

ated Equipment . . . . . . . . . . . . 4-2

4.3.2 Mobilized Equipment . . . . . . . . . . 4-2

4.4 INFORMATIONAL MARKINGS

(OPTIONAL) . . . . . . . . . . . . . 4-4

4.5 COLOR, STYLE AND SIZE OF

MARKINGS . . . . . . . . . . . . . . 4-4

Chapter Page

4.5.1 Use of Reflective Tape, Decals, and

Vinyl Lettering . . . . . . . . . . . . 4-4

4.5.2 Field Numbers . . . . . . . . . . . . . . . 4-5

4.5.3 USAF Legends . . . . . . . . . . . . . . 4-5

4.5.4 Color Numbers . . . . . . . . . . . . . . 4-5

4.5.5 Markings Size . . . . . . . . . . . . . . . 4-5

4.5.6 Tire Pressure/Tow Speed . . . . . . . . 4-5

4.6 MAINTENANCE OF

MARKINGS . . . . . . . . . . . . . . 4-5

4.6.1 Markings Removal . . . . . . . . . . . . 4-5

4.6.2 National Guard Decalcomania . . . . 4-5

4.7 CAUTION/WARNING

MARKINGS . . . . . . . . . . . . . . 4-5

4.7.1 Pintle Hook Caution Marking. . . . . 4-5

4.7.2 Spring Loaded Warning

Marking . . . . . . . . . . . . . . . . . 4-5

4.7.3 Aircraft Towbar Caution

Marking . . . . . . . . . . . . . . . . . 4-5

4.7.4 Tire Pressure/Tow Speed

Markings . . . . . . . . . . . . . . . . 4-5

4.7.5 Personnel Static Discharge

Marking . . . . . . . . . . . . . . . . . 4-5

4.8 FUEL CELL REPAIR SE

IDENTIFICATION. . . . . . . . . . 4-5

5 CORROSION PREVENTION AND CON-

TROL OF HUSH HOUSES . . . . . . . . . . . 5-1

5.1 MATERIALS . . . . . . . . . . . . . . . 5-1

5.1.1 Fastener Replacement . . . . . . . . . . 5-1

5.2 REPAIR . . . . . . . . . . . . . . . . . . . 5-1

5.2.1 Galvanized Steel . . . . . . . . . . . . . 5-1

5.2.2 Carbon Steel . . . . . . . . . . . . . . . . 5-1

5.2.3 Stainless Steel . . . . . . . . . . . . . . . 5-2

5.2.3.1 Type 321 Stainless Steel . . . . . . . . 5-2

5.2.3.4 American Iron and Steel Institute

(AISI) 409 Stainless Steel . . . . . 5-2

5.2.3.7 Sealing . . . . . . . . . . . . . . . . . . . . 5-3

5.3 PRETREATMENT

COMPOUNDS . . . . . . . . . . . . 5-3

5.3.1 Rust Remover 81287 (Naval

Jelly) . . . . . . . . . . . . . . . . . . . 5-3

5.4 PRIMERS. . . . . . . . . . . . . . . . . . 5-3

5.4.1 Organic Zinc-Rich Primers . . . . . . 5-3

5.4.2 Inorganic Zinc-Rich Primers . . . . . 5-3

5.5 PAINTING . . . . . . . . . . . . . . . . . 5-3

5.5.1 Structural Corrosion Protection. . . . 5-3

5.5.2 Camouflage Requirements . . . . . . . 5-3

5.6 INORGANIC ZINC PRIMED

SURFACES. . . . . . . . . . . . . . . 5-4

5.6.1 Primer Requirements on the Door

Frame Beams, Support Beams, and Exhaust Tube. . . . . . . . . . . 5-4

5.7 GALVANIZED SURFACES. . . . . . 5-4

TO 35-1-3

iii

5.7.1 Roof. . . . . . . . . . . . . . . . . . . . . . 5-4

5.7.2 Walls and Doors . . . . . . . . . . . . . 5-5

6 CORROSION PREVENTION AND CON-

TROL OF NOISE SUPPRESSOR SYS-

TEMS (NSS) . . . . . . . . . . . . . . . . . . . . . 6-1

6.1 GENERAL . . . . . . . . . . . . . . . . . 6-1

6.2 MATERIALS . . . . . . . . . . . . . . . 6-1

6.3 FASTENER REPLACEMENT . . . . 6-1

6.4 STRUCTURAL REPAIR. . . . . . . . 6-1

6.4.1 Structural Repair Carbon Steel . . . . 6-1

6.4.2 Galvanized Steel . . . . . . . . . . . . . 6-1

6.4.3 AISI 409 Stainless Steel . . . . . . . . 6-1

6.5 SEALING. . . . . . . . . . . . . . . . . . 6-2

6.6 PRIMERS. . . . . . . . . . . . . . . . . . 6-2

6.6.1 Organic Zinc-Rich Primers . . . . . . 6-2

6.6.2 MIL-PRF-23236, Type I, Class

3 . . . . . . . . . . . . . . . . . . . . . . 6-2

6.6.3 Heat Resistant Primer Briner

2905. . . . . . . . . . . . . . . . . . . . 6-2

6.6.4 Heat Resistant Silicone Coating -

Briner 2986 . . . . . . . . . . . . . . . 6-2

6.6.5 High Temperature Resistant Silicone

Coating - Briner 4765 . . . . . . . . 6-3

6.6.6 High Temperature Resistant Silicone

Coating Thurmalox 270-18 . . . . 6-3

Chapter Page

7 SOUTHWEST ASIA OPERATIONS AND

ENVIRONMENTS . . . . . . . . . . . . . . . . . 7-1

7.1 GENERAL . . . . . . . . . . . . . . . . . 7-1

7.1.1 Environmental Effects . . . . . . . . . . 7-1

7.1.1.1 Soils and Humidity. . . . . . . . . . . . 7-1

7.2 SE SWA AOR

DEPLOYMENT. . . . . . . . . . . . 7-2

7.2.1 Pre-deployment . . . . . . . . . . . . . . 7-2

7.2.2 Deployment Location . . . . . . . . . . 7-2

7.2.2.1 SE Units Requiring Additional

Cleaning . . . . . . . . . . . . . . . . . 7-2

7.2.3 Maintenance Touch-Up

Painting . . . . . . . . . . . . . . . . . 7-3

7.2.3.1 Temporary Coating Repair . . . . . . . 7-4

7.2.3.2 Permanent Authorized

Touch-Ups . . . . . . . . . . . . . . . 7-4

7.2.4 Equipment Storage . . . . . . . . . . . . 7-4

APPENDIX A EQUIPMENT AND CONSUM-

ABLE MATERIALS USED FOR CORRO-

SION CONTROL . . . . . . . . . . . . . . . . . . . A-1

A.1 EQUIPMENT AND CONSUM-

ABLE MATERIALS. . . . . . . . . A-1

TO 35-1-3

iv

LIST OF ILLUSTRATIONS

Number PageTitle

1-1 Diagram of a Simplified Corrosion Cell and an Example of Raised Corrosion Product . . . . . . . . . . . . . . . . . . . . . . 1-2

1-2 Galvanic Series of Metals and Alloys . . . 1-3 1-3 Corrosion Accelerated by Condensed

Moisture . . . . . . . . . . . . . . . . . . . . . 1-6 1-4 Open Cell Foam and Resulting

Corrosion . . . . . . . . . . . . . . . . . . . . 1-6 1-5 View of the Results of Microbial Induced

Corrosion . . . . . . . . . . . . . . . . . . . . 1-7 1-6 Example of Uniform Etch . . . . . . . . . . . 1-9 1-7 Example of Galvanic Corrosion - Steel

Hinge Bolted to an Aluminum Door. . . . . . . . . . . . . . . . . . . . . . . . 1-9

1-8 Example of Pitting Corrosion . . . . . . . . . 1-10 1-9 Illustration of an Intergranular Corrosion

Cell . . . . . . . . . . . . . . . . . . . . . . . . 1-10 1-10 Example of Exfoliation Corrosion . . . . . . 1-11 1-11 Examples of Concentration/Crevice

Corrosion . . . . . . . . . . . . . . . . . . . . 1-11 1-12 Example of Exfoliation Corrosion . . . . . . 1-11 1-13 Example of Filiform Corrosion . . . . . . . . 1-13 1-14 Illustration of a Fretting Corrosion

Cell . . . . . . . . . . . . . . . . . . . . . . . . 1-13 3-1 Example of Standing Water Due to Inad-equate Drainage Provisions . . . . . . . . 3-13 3-2 Hollow Member Drain Hole

Configuration . . . . . . . . . . . . . . . . . . 3-13 3-3 Hollow Member Weld-Nut

Configuration . . . . . . . . . . . . . . . . . . 3-14 3-4 Corrosion Under Data Plate . . . . . . . . . . 3-24 4-1 NATO Liquid Oxygen Servicing

Markings. . . . . . . . . . . . . . . . . . . . . 4-1 4-2 NATO Liquid Nitrogen Servicing

Markings. . . . . . . . . . . . . . . . . . . . . 4-2 4-3 Sample Mobility Placard . . . . . . . . . . . . 4-3 4-4 1,500 LB Utility Crane . . . . . . . . . . . . . 4-6 4-5 ACE Air Conditioner MC1A, Diesel . . . . 4-8 4-6 AF/M27M-1 Pumping Unit, Hydraulic, Diesel Driven. . . . . . . . . . . . . . . . . . 4-10 4-7 AF/M32T-1 Cabin Leakage Tester . . . . . . 4-12 4-8 Aircraft Oxygen Servicing Cart. . . . . . . . 4-14 4-9 A/M24T-8 Load Bank . . . . . . . . . . . . . . 4-16 4-10 A/M32A-60A Gas Turbine Generator. . . . 4-18 4-11 A/M32A-86 Generator, Diesel . . . . . . . . 4-20 4-12 A/M32A-95 Compressor, Gas Turbine, Trailer Mounted . . . . . . . . . . . . . . . . 4-22 4-13 A/M32C-10C/10D Air Conditioner

Set . . . . . . . . . . . . . . . . . . . . . . . . . 4-24 4-14 A/M32C-5 Air Conditioner Set . . . . . . . . 4-26 4-15 Auxiliary Ground Power Unit

(AGPU) . . . . . . . . . . . . . . . . . . . . . 4-28

Number PageTitle

4-16 B-1/B-2 Air Conditioner, Trailer Mounted . . . . . . . . . . . . . . . . . . . . . 4-30

4-17 B-4 Maintenance Stand . . . . . . . . . . . . . 4-32 4-18 B-5 Maintenance Stand . . . . . . . . . . . . . 4-34 4-19 B-2 Maintenance Stand . . . . . . . . . . . . . 4-36 4-20 B-7/B-1 Maintenance Stand . . . . . . . . . . 4-38 4-21 B809A Generator Set . . . . . . . . . . . . . . 4-40 4-22 C-1 Maintenance Stand . . . . . . . . . . . . . 4-42 4-23 Spraying Unit, Corrosion Control Wash

Cart . . . . . . . . . . . . . . . . . . . . . . . . 4-44 4-24 EPU-6 Aircraft Power Supply. . . . . . . . . 4-46 4-25 FDECU-3 Environmental Control

Unit . . . . . . . . . . . . . . . . . . . . . . . . 4-48 4-26 Fuel Bowser 400 Gallon . . . . . . . . . . . . 4-50 4-27 H-1 Heater . . . . . . . . . . . . . . . . . . . . . 4-52 4-28 HDU-13M Heater . . . . . . . . . . . . . . . . . 4-54 4-29 Hydraulic Cart . . . . . . . . . . . . . . . . . . . 4-56 4-30 Jack, Hydraulic 10 - 30 Ton . . . . . . . . . . 4-58 4-31 Jack, 35 Ton, Axle . . . . . . . . . . . . . . . . 4-60 4-32 Liquid Cooling Service (LCS) Cart . . . . . 4-62 4-33 Liquid Oxygen Cart . . . . . . . . . . . . . . . 4-64 4-34 LN2 Liquid Nitrogen Cart . . . . . . . . . . . 4-66 4-35 MC-1A High Pack Air Compressor . . . . . 4-68 4-36 MA-3D Air Conditioner. . . . . . . . . . . . . 4-70 4-37 MC-2A Air Compressor. . . . . . . . . . . . . 4-72 4-38 MC-7 Air Compressor . . . . . . . . . . . . . . 4-74 4-39 MD-1 Towbar . . . . . . . . . . . . . . . . . . . 4-76 4-40 MEP Generators . . . . . . . . . . . . . . . . . . 4-78 4-41 MHU-83C/E Bomblift Truck . . . . . . . . . 4-80 4-42 MJ-1B Bomblift Truck . . . . . . . . . . . . . 4-82 4-43 Hydraulic Test Stand . . . . . . . . . . . . . . . 4-84 4-44 Light Cart, FL-1D . . . . . . . . . . . . . . . . 4-86 4-45 NF-2D Light Cart, Diesel . . . . . . . . . . . 4-88 4-46 Oil Cart . . . . . . . . . . . . . . . . . . . . . . . 4-90 4-47 Purging Unit GSU-62M LOX

Storage . . . . . . . . . . . . . . . . . . . . . . 4-92 4-48 Radome Dolly . . . . . . . . . . . . . . . . . . . 4-94 4-49 Self-Generating Nitrogen Cart . . . . . . . . 4-96 4-50 Service Cart. . . . . . . . . . . . . . . . . . . . . 4-98 4-51 Trielectron Generator . . . . . . . . . . . . . . 4-100 4-52 Universal Maintenance Stand . . . . . . . . . 4-102 4-53 New Generation Heater . . . . . . . . . . . . . 4-106 5-1 Angle Iron Sealant Application . . . . . . . . 5-2

7-1 SWA AOR. . . . . . . . . . . . . . . . . . . . . . 7-1

7-2 Sand/Dust Intrusion . . . . . . . . . . . . . . . 7-2 7-3 Residue from Salts Caused by

Condensation . . . . . . . . . . . . . . . . . . 7-2 7-4 Locally Manufactured Permeable

Covers . . . . . . . . . . . . . . . . . . . . . . 7-3 7-5 Wire Bundle Sand/Dust

Accumulation. . . . . . . . . . . . . . . . . . 7-3 v

Number PageTitle

1-1 Corrosion of Metals - Type of Attack and Appearance of Corrosion Products . . . 1-15

2-1 Wash Interval Based on Corrosion Sever-ity Zones. . . . . . . . . . . . . . . . . . . . . 2-2

2-2 Authorized Cleaning Materials . . . . . . . . 2-8 2-3 Authorized HPW Equipment . . . . . . . . . 2-17 3-1 Authorized Coating Systems . . . . . . . . . 3-6 3-2 SE Scoring/Category Criteria . . . . . . . . . 3-10 3-3 Pretreatment Instructions . . . . . . . . . . . . 3-16 3-4 Metalization Material Sources of

Supply . . . . . . . . . . . . . . . . . . . . . . 3-21

Number PageTitle

4-1 Mobility Placard Construction Information . . . . . . . . . . . . . . . . . . . 4-3

4-2 Mobility Placard Stencil Requirements . . . . . . . . . . . . . . . . . . 4-4

5-1 Hush House Coating Chart. . . . . . . . . . . 5-3 A-1 Equipment and Consumable Materials

List . . . . . . . . . . . . . . . . . . . . . . . . A-1

TO 35-1-3

LIST OF TABLES

vi

FOREWORD

1 PURPOSE.

The purpose of this manual is to provide information neces-sary to prevent or minimize the impact of corrosion on Sup-port Equipment (SE). This manual is designed to provide basic corrosion principal, theory, identification, prevention and control information to enable SE technicians to differen-tiate between the different types of corrosion in order to identify the appropriate temporary repair materials and pro-cesses. This technical order is specific to SE; however, for areas not covered in this manual, or expanded information on a particular material or process, technicians or contractors should refer to TO 1-1-691, “Aircraft Weapon Systems Cleaning and Corrosion Control”. For additional guidance, refer to TO 1-1-8, “Application and Removal of Organic Coatings, Aerospace and Non-Aerospace Equipment”, and TO 1-1-689, “Avionic Cleaning, and Corrosion Prevention/ Control”.

2 SCOPE.

This manual is designed to provide basic information to be used by Organizational/Unit, Intermediate, and Depot levels of maintenance. This manual shall also be used to provide guidance for corrosion prevention and control activities of contracted maintenance inspection, repair, and overhaul of SE. If conflicting instructions occur, the end item manual takes precedence over this manual. Conflicts in resolving any conflicting materials and processes application requirements shall be referred to the Air Force Corrosion Prevention and Control Office, AFRL/RXSSR, Robins AFB, GA. Conflicts regarding all other criteria in this manual shall be referred to WR-ALC, Robins AFB, GA for resolution.

2.1 Chapter 1 Description. This chapter provides the ba-

sic information needed by SE technicians to accurately iden-tify the causes, types of corrosion and how to minimize the factors that cause and accelerate corrosion. This chapter also provides procedures for the SE technicians to be able to treat corrosion in the early stages.

2.2 Chapter 2 Description. This chapter establishes the

recommended SE wash cycles based on location; provides a listing and description of authorized cleaning compounds;

and lists specific cleaning processes for SE.

2.3 Chapter 3 Description. This chapter provides the SE

technician with the coating requirements authorized coating systems, sealing requirements, and corrosion preventive compound applications. It also provides the only authorized colors for USAF SE.

2.4 Chapter 4 Description. This chapter displays autho-

rized markings and their locations on SE.

2.5 Chapter 5 Description. This chapter covers the mate-

rials and processes for construction and maintenance of Hush Houses.

2.6 Chapter 6 Description. This chapter covers the mate-

rials and processes for Noise Suppressor Systems (NSS).

2.7 Chapter 7 Description. This chapter covers opera-

tions unique to the Southwest Asia Region.

2.8 Appendix A Description. This appendix provides a

list of consumable material authorized for use on SE.

3 ABBREVIATIONS.

All abbreviations used in this manual are in accordance with ASME Y14.38, Abbreviations and Acronyms for Use on Drawings and Related Documents.

AF Air Force AFI Air Force Instructions AFOSH Air Force Office of Safety and Health AFRL/RXSSR Air Force Corrosion Prevention and Con-trol Office AFTO Air Force Technical Order AISI American Iron and Steel Institute AOR Area of Responsibility BBE Base Bioenvironmental Engineer BG Bag BOD Biochemical Oxygen Demand BX Box C Celsius CA Cartridge CAGE Commercial and Government Entity CARC Chemical Agent Resistant Coating cc Cubic Centimeter CFE Contractor Furnished Equipment CN Can CO Container CPC Corrosion Preventive Compound CRES Corrosion Resistant Steel CS Case DO Dissolved Oxygen DoD Department of Defense DFT Dry Film Thickness DR Drum DZ Dozen EA Each ESD Electrostatic Discharge vii

F Fahrenheit ft Feet GL Gallon GPM Gallons Per Minute HP Horsepower HPW High-Pressure Water I&S Interchangeability and Substitution lbs Pounds ID Inside Diameter

in. Inch KT Kit LOI Local Operating Instructions MAP Military Assistance Program MIG Gas Metal-Arc MSDS Material Safety Data Sheet MWAS Metallization Process Metal Wire Arc

Spray MX Thousand NACE National Association of Corrosion Engi-neers NATO North Atlantic Treaty Organization NSN National Stock Number NSS Noise Suppressor Systems OD Outside Diameter OSHA Occupational Safety and Health Adminis-tration oz Ounce PG Package pH Potential of Hydrogen PM Preventive Maintenance PN Part Number PPE Personal Protective Equipment PSI Pounds Per Square Inch PSIG Pounds Per Square Inch Gauge PT Pint QPL/QPD Qualified Products List/Database QT Quart REF Reference RDS Rapid Desealing System RH Relative Humidity RO Roll RTV Room Temperature Vulcanizing SC Sealing Compound SCC Stress Corrosion Cracking SCFM Standard Cubic Feet Per Minute SE Support Equipment SSDC Steel Structure Painting Council SWA Southwest Asia TDS Total Dissolved Solids TIG Gas Tungsten Arc TOMA Technical Order Management Agency

TU Tube USAF United States Air Force VOC Volatile Organic Compound

4 RELATED PUBLICATIONS.

The following publications contain information in support of this technical manual.

List of Related Publications

Number Title ASME Y14.38 Abbreviations and Acronyms for Use on Drawings and Related Documents

DODI 5330.03_AFI 33-395 Document Automation and Production Service

(DAPS)

MIL-HDBK-263 Electrostatic Discharge Con-trol Handbook for Protec-tion of Electrical and Electronic Parts, Assem-blies and Equipment

TO 00-5-1-WA-1 Air Force Technical Order System

TO 00-25-195-WA-1 Source, Maintenance, and Recoverability Coding of Air Force Weapons, Sys-tems, and Equipment

TO 00-25-234-WA-1 General Shop Practice Re-quirements for the Repair, Maintenance, and Test of Electrical Equipment

TO 1-1-3 Inspection and Repair of Aircraft Integral Tanks and Fuel Cells

TO 1-1-691 Aircraft Weapons Systems - Cleaning and Corrosion Control

TO 1-1-8 Application and Removal of Organic Coatings, Aero-space and Non-Aerospace Equipment

TO 35C2-3-1-426WC-4-20-1 Periodic Inspection Work Cards - Diesel Engine Driven Generator Sets A/M32A-86 Series

TO 36-1-191 Technical and Managerial Reference for Motor Ve-hicle Maintenance

TO 42B-1-23 Management of Recoverable and Waste Liquid Petro-leum Products

5 RECORD OF APPLICABLE TIME COMPLIANCE

TECHNICAL ORDERS (TCTOS).

viii

List of Time Compliance Technical Orders

TCTO

Number

TCTO

Title

TCTO

Date

None

6 HARDNESS CRITICAL ITEMS (HCI).

The HCI symbol ( ) establishes special re-quirements limiting changes and substitutions and that the specific parts listed must be used to ensure hardness is not degraded.

If included, items with nuclear survivability requirements are marked with the HCI symbol ( ). All changes to, or pro-posed substitutions of, HCIs must be approved by the ac-quiring activity.

7 ELECTROSTATIC DISCHARGE SENSITIVE

(ESDS) ITEMS.

All ESDS parts shall be handled in accordance with the ESDS device handling procedures in TO

00-25-234-WA-1.

If included, items containing ESDS parts are marked with the ESDS symbol ( ).

8 CHANGE RECOMMENDATIONS.

Recommendations proposing changes to this technical order shall be submitted on an AFTO Form 22 in accordance with TO 00-5-1-WA-1. Forward completed AFTO Form 22 to the Technical Order Management Agency (TOMA) at:

robins.ce.afto22@robins.af.mil. Changes should not be sub-mitted for Chapter 4 marking legends and illustrations. Mark-ing and illustrations in Chapter 4 are for reference use only.

AFTO 22s addressing specific markings of SE should be directed to the end-item specific technical orders.

ix/(x blank)

SAFETY SUMMARY

1 GENERAL SAFETY INSTRUCTIONS.

This manual describes physical and/or chemical processes which may cause injury or death to personnel, or damage to equipment, if not properly followed. This safety summary includes general safety precautions and instructions that must be understood and applied during operation and maintenance to ensure personnel safety and protection of equipment. Prior to performing any specific task, the WARNINGs, CAU- TIONs, and NOTEs included in that task shall be reviewed and understood. The safety precautions in AFI 91-203 and OSHA Standard 1910.107 are applicable to the operation of paint shops and spray-painting equipment and shall be fol-lowed during cleaning and repainting of SE.

2 WARNINGS, CAUTIONS, AND NOTES.

WARNINGs and CAUTIONs are used in this manual to highlight operating or maintenance procedures, practices, conditions, or statements which are considered essential to protection of personnel (WARNING) or equipment (CAU- TION). WARNINGs and CAUTIONs immediately precede the step or procedure to which they apply. WARNINGs and CAUTIONs consist of four parts: heading (WARNING, CAUTION, or icon), a statement of the hazard, minimum precautions, and possible results if disregarded. NOTEs are used in this manual to highlight operating or maintenance procedures, practices, conditions, or statements which are not essential to protection of personnel or equipment. NOTEs may precede or follow the step or procedure, depending upon the information to be highlighted. The headings used and their definitions are as follows:

Highlights an essential operating or maintenance procedure, practice, condition, statement, etc., which if not strictly observed, could result in in-jury to, or death of, personnel or long term health hazards.

Highlights an essential operating or maintenance procedure, practice, condition, statement, etc., which if not strictly observed, could result in dam-age to, or destruction of, equipment or loss of mis-sion effectiveness.

NOTE

Highlights an essential operating or maintenance procedure, condition, or statement.

3 MATERIALS HANDLING.

3.1 Personnel Hazards. Many of the materials and pro-

cedures outlined in this technical order are potentially haz-ardous to personnel, if used improperly. When using chemi-cals such as paint strippers, cleaning compounds, conversion coatings, and solvents, follow the correct procedures and wear appropriate protective gear to prevent injury to person-nel. Read the appropriate Material Safety Data Sheet (MSDS), manufacturer’s instructions and be familiar with related warnings and cautions in this technical order prior to using any material. Misuse of certain materials can also damage parts or cause corrosion. Refer to DOD 6050.5-LR, Hazardous Material Information System, FED STD 313, Material Safety Data, Transportation Data, and Disposal Data for Hazardous Material Furnished to Government Activities, or the appropriate systems command documents for the han-dling, storage, and disposal of hazardous materials. When in doubt, contact the local safety office, base bioenvironmental office, or regional medical center for guidance.

3.2 Environmental Hazards. Many of the materials and

procedures outlined in this technical order are also poten-tially hazardous to the environment. Wherever possible, methods for preventing pollution, minimizing waste, and us-ing less toxic materials are given. Consult the base bioenvi-ronmental office for information about the handling, storage, and disposal of hazardous waste.

4 GENERAL PRECAUTIONS.

The following general safety precautions are not related to any specific procedure and therefore do not appear elsewhere in this technical manual. These are general safety precau-tions and instructions people must understand and apply dur-ing many phases of operation and maintenance to ensure personal safety and health and the protection of Air Force property.

4.1 Live Circuits. Operating personnel must observe all

safety requirements at all times. Do not replace components or make adjustments inside equipment with the electrical supply turned on. Under certain conditions, danger may exist even when the power control is in the off position due to charges retained by capacitors. To avoid injuries, always re-move power, discharge, and ground a circuit before touching

it. Adhere to all lock out/tag out requirements.

4.2 Resuscitation. Personnel working with or near dan-

gerous voltage shall be trained in modern methods of resus-citation. Information and training sources may be obtained from the Director of Base Medical Services.

xi

4.3 Finger Rings/Jewelry. Finger rings have caused many

serious injuries. Remove rings, watches and other metallic objects that may cause shock or burn hazards. Unless spe-cifically allowed by shop safety procedures, remove finger rings during all maintenance activity.

4.4 Compressed Air. Use of compressed air can create an

environment of propelled particles. Do not direct air streams towards yourself or other personnel. Air pressure shall be reduced to less than 30 Pounds Per Square Inch Gauge (PSIG) and used with effective chip guarding and personal protective equipment.

4.5 Dangerous Pressures. Care must be taken during

testing to ensure that all test connections are proper and tight.

All system components must be compatible with applied pressure. Personnel must be protected by a safety shield or located at a distance sufficient to prevent injury.

5 PERSONAL PROTECTIVE EQUIPMENT (PPE).

If unique local conditions make compliance with the protec-tive clothing or other occupational health requirements speci-fied in this manual unnecessary or impractical, obtain an evaluation of the operation from the Bioenvironmental Engi-neer. The Bioenvironmental Engineer or Base Safety Office will determine the required precautions and approved PPE.

6 CLEANERS/CHEMICALS/PAINTS/PRIMERS.

Some cleaners, chemicals, paints, and primers have adverse effects on skin, eyes, and the respiratory tract. Observe manufacturer’s warning labels, Material Safety Data Sheet (MSDS) and other instructions for proper handling, storage, and disposal; and current safety directives. Use only in au-thorized areas.

7 ELECTROSTATIC DISCHARGE (ESD).

Certain circuit card assemblies and their components will be damaged by seemingly undetectable electrostatic discharge.

Care must be exercised during handling/repair of those items.

Use Electrostatic Discharge (ESD) precautionary procedures outlined in TO 00-25-234, General Shop Practice Require-ments for Repair, Maintenance and Test of Electrical Equip-ment, and MIL-HDBK-263, Electrostatic Discharge Control Handbook for Protection of Electrical and Electronic Parts, Assemblies and Equipment.

xii

CHAPTER 1

CORROSION THEORY, IDENTIFICATION, CAUSES AND EFFECTS

1.1 PURPOSE.

The purpose of this chapter is to provide Support Equipment (SE) maintenance personnel with the basic knowledge nec-essary to understand the causes of corrosion, identify the different types of corrosion that will in-turn help minimize corrosion damage through prevention and early detection and treatment. To help prevent corrosion, SE technicians must first need to understand corrosion causes and effects and be able to recognize there are several types of corrosion with different preventive measures. This chapter is an introduc-tion to corrosion theory, the causes of corrosion and the fac-tors that influence its development. The various forms of corrosion and the effect of corrosive environments normally on SE are also described in this chapter.

1.2 DEFINITION OF CORROSION.

Corrosion is the electrochemical deterioration of a metal be-cause of its chemical reaction with the surrounding environ-ment. This reaction occurs because of the tendency of metals to return to their naturally occurring states, usually oxide or sulfide ores. For example, iron in the presence of moisture and air will return to its natural state, iron oxide or rust.

Aluminum and magnesium form corrosion products that are white oxides or hydroxides. When corrosion occurs, water is usually present in some form (e.g., humidity, moisture, con-densation, rain, salt spray, etc.), acting as an electrolyte and reacting chemically with metal surfaces.

1.3 CHEMICAL DEFINITIONS.

1.3.1 Atom. The smallest unit of an element. There are

more than 100 elements, including metals (such as alumi-num, magnesium, iron, nickel, titanium, cadmium, chro-mium, copper, and carbon) and non-metals (such as hydro-gen, oxygen, sulfur, and chlorine).

1.3.2 Electron. A negatively charged particle much

smaller than an atom. An electrical current occurs when electrons are forced to move through metal conductors. Elec-trons also flow through water solutions, but only in the pres-ence of ions.

1.3.3 Ions. Atoms or groups of atoms bound together that

is either positively or negatively charged. An electrical cur-rent occurs when ions are forced to move through water so-lutions. Ions cannot move through metal conductors.

1.3.4 Electrolyte. A liquid solution (usually water) con-

taining ions. Salt water is an electrolyte, an aqueous (i.e., water) solution of sodium ions and chloride ions.

1.4 THEORY OF CORROSION.

A corrosion cell is much like a battery. When a metal cor-rodes, the metal atoms lose electrons and become metal ions in an electrolyte solution. The positively charged metal ions can combine with negatively charged ions to form corrosion products, such as metallic chlorides, oxides, hydroxides, and sulfides. Four conditions must exist before this type of cor-rosion can occur.

1.4.1 Anode. A metal must be present that has a tendency

to corrode. The corroding metal is known as the anode.

1.4.2 Cathode. A dissimilar conductive material (the cath-

ode) that has less of a tendency to corrode than the anode must be present. Examples include a different metal, a pro-tected part of the same metal, or conductive plastics/compos-ite.

1.4.3 Electrolyte. A conductive liquid (electrolyte) must

connect the anode and cathode so that ions can carry electri-cal current between them.

1.4.4 Electrical Path. Electrical contact between the an-

ode and cathode (usually in the form of metal-to-metal con-tact) must exist so that electrons can move from the anode, where they are released, to the cathode. Eliminating any one of these four conditions, illustrated in Figure 1-1, will stop corrosion. For example, a paint film on a metal surface will prevent the conducting liquid (electrolyte) from connecting the anode and cathode, thereby stopping the electric current.

Another example is when two connected dissimilar metal parts placed in pure water corrode very slowly because of the lack of ions to conduct the electric current. In seawater, the corrosion reaction is accelerated by a factor of 1,000 or more.

1-1

1.5 DEVELOPMENT OF CORROSION.

1.5.1 Corrosion Origination Locations. All corrosive at-

tacks begin on the surface of metals whether it is the inside of a bolt hole, border of a metal crystal, hand rail interior or bottom of a frame. If allowed to progress, corrosion can pen-etrate into and through the metal. When corrosion products form, they often precipitate onto the corroding surface as a powdery or scaled deposit. Other evidence of corrosion is the bulging/blistering of the metal surfaces. Thin film corro-sion forms on electrical contact points and pins may appear as a tarnish, or powdery deposit on the metal surface.

1.5.2 Corrosion Under Painted Surfaces. Paint coatings

can mask the initial stages of corrosion. Because corrosion products occupy more volume than the original metal, fre-quently inspect paint surfaces for irregularities such as blis-ters, flakes, chips, and lumps.

Figure 1-1. Diagram of a Simplified Corrosion Cell and an Example of Raised Corrosion Product

1-2

Figure 1-2. Galvanic Series of Metals and Alloys

1-3

1.6 FACTORS INFLUENCING CORROSION.

Both natural and man-made environments cause corrosion of SE. Natural conditions that affect the corrosion process are moisture, temperature, salt atmospheres, ozone, sand, dust, solar radiation, insects and birds, and microorganisms. Man-made conditions that affect the corrosion process are indus-trial pollution, manufacturing operations, storage conditions, and shipment. By understanding these conditions, mainte-nance personnel will be better able to prevent SE damage.

Factors that influence metal corrosion and the rate at which it occurs are outlined in Figure 1-2.

1.6.1 Type of Metal. The metals most commonly used in

SE construction are aluminum, steel, and to some extent magnesium. Cadmium, nickel, chromium, and silver are sometimes used as protective plating. Metals have a wide range of corrosion resistance. The most active metals (i.e., those that tend to lose electrons easily), such as magnesium and aluminum, corrode easily and are listed at the top of Figure 1-2. The most noble metals (i.e., those that do not lose electrons easily), such as gold and silver, do not corrode easily and are listed at the bottom of Figure 1-2.

1.6.2 Dissimilar Metal Coupling (Galvanic Corrosion).

When two dissimilar metals make electrical contact in the presence of an electrolyte, the rate at which corrosion occurs depends on the difference in their location on the galvanic scale (see Figure 1-2). The greater the distance between the metals, the faster corrosion occurs. For example, magnesium corrodes very quickly when coupled with gold in a humid atmosphere. However, pure aluminum corrodes very slowly, if at all, when in contact with cadmium. It is essential in the repair of SE that compatible metals and metal fasteners, washers, etc., be selected for repair and refurbishment pro-cesses. If dissimilar metal coupling must occur due to the equipment design or configuration, contact the appropriate system equipment specialist for the appropriate processes and materials to insulate the incompatible metals.

1.6.2.1 Graphite or carbon fiber composites are materials

which consist of reinforcing fibers in a matrix made of or-ganic resin, usually epoxy. They are an important class of SE construction materials because of their high strength-to-weight ratios and high stiffness. Although graphite or car-bon/carbon composites appear as a plastic, the graphite ma-terial is considered a metal. Care should be exercised when attaching fasteners through the fibers. Use the appropriate sealant to insulate the composite from the metal parts.

1.6.2.2 Since carbon is the least active metal in the gal-

vanic series, it will accelerate the corrosion of any metal to which it is coupled. Insulation, with sealant or other noncon-ductive coatings, between graphite or carbon epoxy compos-ites and other metals surfaces or fasteners is necessary to prevent dissimilar metal attack on the attached part.

1.6.3 Anode and Cathode Surface Area. The rate of

galvanic corrosion also depends on the size of the parts in contact. If the surface area of the corroding metal (the an-ode) is smaller than the surface area of the less active metal (the cathode), corrosion will be rapid and severe. However, if the corroding metal is larger than the less active metal, corrosion will be slow and superficial. For example, an alu-minum fastener in contact with a relatively nonreactive Monel structure may corrode severely, while a Monel bracket secured to a large aluminum member would result in a rela-tively superficial attack on the aluminum.

1.6.4 Climate. Warm, moist air, typically found in tropical

climates, tends to accelerate corrosion because of the higher concentration of water vapor in the air. Additionally, high temperature environments tend to produce more rapid corro-sion because of accelerated chemical reactions. Conversely, cold dry air, typically found in colder regions of the world, tends to slow corrosion rates due to less water vapor in the air. Corrosion does not occur in very dry conditions. For this reason, desiccants or dehumidification systems are placed in, or connected to shipping or storage containers to create very dry local environments. The equipment’s proposed opera-tional environments and established corrosion prevention and control optimal design parameters should be considered in SE design and procurement.

1.6.4.1 Desert. Hot, wind-swept deserts create a severe

maintenance problem because powdery dust can penetrate even supposedly sealed components. Typically, desert condi-tions are thought to have low humidity and rainfall. How-ever, there are areas of the world considered as desert with high daytime temperatures, moderate to low night time tem-peratures, high humidity (in areas such as the Persian Gulf), ultraviolet radiation, and fine dust. These conditions pose the most serious, destructive elements of the desert climate due to the wide range of conditions experienced daily.

1.6.4.2 Temperate Zones. The temperate or intermediate

climate zone encompasses most of the North American and European continents. These areas at various times of the year may approximate the extremes of polar, desert, or tropical temperatures and humidity. The temperate zone temperatures range from -25 °Fahrenheit (F) to +59 °F (-32 °Celsius (C) to +15 °C) in the winter and from +59 °F to +125 °F (+15 °C to +52 °C) in the summer. The relative humidity (RH) also fluctuates between five and 100%. The most critical ar-eas are coastal locations, during the warm periods of the year in which the relative humidity approaches 100% RH at night and the air has high concentrations of salt. Moisture from this salt laden air can condense on equipment during early evening and morning hours, thereby causing serious corrosion. Because of its relatively mild temperatures, the temperate zone is also the most heavily populated. Conse-quently the smoke, smog, ozone, and corrosive fumes asso-ciated with heavy industry are also found there.

1.6.4.3 Tropics. One of the greatest challenges to SE

manufacturing industries is to the design equipment that is protected from corrosion and deterioration in the continual heat and humidity of tropical climates. Even though they encompass only a small portion of the earth’s land area, the tropics demand the greatest amount of consideration from

1-4 the standpoint of corrosion treatment and control. Relative humidity of up to 100% RH at ambient air temperatures of 85 °F (29 °C) and above create a formidable threat of corro-sion. When high humidity and temperature conditions are combined with saltladen air, the corrosive environment be-comes extremely severe. The critical combination of high temperatures, condensation, high relative humidity, and con-taminants such as salt and sand may cause premature struc-tural failure of equipment due to corrosion. Deterioration of the materials used in electronic equipment may also be ac-celerated. Thin film corrosion on electrical contact points and pins act as insulators to electrical current adversely af-fecting the operations of SE.

1.6.4.3.1 Factors of Influence in Tropical Environ-

ments. Tropical environments are noted for long periods of heavy rainfall, during which 100 inch (in.) or more of rain may fall. Extended periods of high heat and humidity con-tribute to rapid corrosion of metals, cracking and flaking of rubber and plastic materials, and deterioration of seals.

Equipment, whether stored or in use, requires special protec-tive containers/measures and frequent preventive mainte-nance. Microorganisms multiply excessively in tropical en-vironments and attack many non-metallic materials. Many items become covered with fungi in a matter of hours. Elec-tronic equipment requires special efforts for effective opera-tion in the tropics.