TO 35-1-3 For Reference Only.pdf

TO 35-1-3

TECHNICAL MANUAL

CORROSION PREVENTION AND CONTROL,

CLEANING, PAINTING, AND MARKING

OF USAF SUPPORT EQUIPMENT (SE)

APR 1 8 2008

DISTRIBUTION STATEMENT A - Approved for public release; distribution is unlimited (WR-ALC/PA Public Affairs Certification Number 05-07173).

Other requests for this documeni shall be referred to 584 CBSS/GBHDE. Robins AFB, GA 31093. Questions concerning technical content shall be referred to AFRL/MLS-OLR.

Published Under Authority of Ihe Secretary of the Air Force

1 SEPTEMBER 2006 change 3 - 26 February 2008

Solicitation #F1W2E89096AQ01 Attachment #8

| LIST OF EFFECTIVE PAGEJT- 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 DESTROY SUPERSEDED PAGES.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 minia ture pointing hands. Changes to wiring diagrams are indicated by miniature pointing hands or by shaded areas. A vertical line running the length of a fig ure in trie outer margin of the page indicates that the figure is being added.

Dates of issue for original and changed pages are:

Original 0 1 September 2006

Change I 5 June 2007 Change 2 21 August 2007

Change 3 26 February 2008

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USAF

TABLE OF CONTENTS

■V"

Chapter Page

LIST OF ILLUSTRATIONS iv

LIST OF TABLES v

FOREWORD vii

SAFETY SUMMARY ix

1 CORROSION THEORY, IDENTIFICATION,

CAUSES AND EFFECTS 1-1

1.1 Purpose l-l

1.2 Definition of Corrosion l-l

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 ofCorrosion 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 1-1

1.5.1 Corrosion Origination Locations 1 -1

1.5.2 Corrosion Under Painted Surfaces 1-2

1.6 Factors Influencing Corrosion 1-2

1.6.1 Type of Metal 1-2

1.6.2 Dissimilar Metal Coupling (Galvanic

Corrosion) 1-2

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

1.6.4.3.1 Factors of Influence in Tropical

Environments 1 -4

1.6.5 Heat Treatment and Grain Direction 1 -4

1.6.6 Electrolytes 1-4

1.6.7 Microbial Induced/Influenced

Corrosion 1-6

1.6.8 Mechanical Stress 1-7

1.6.9 Time 1-7

Chapter Page

1.6.10 Manufacturing 1-7

1.6.11 Storage 1 -7

1.6.12 Degradation of Non-metals 1-7

1.6.13 Preventive Maintenance (PM) 1 -7

1.7 Types of Corrosion 1-8

1.7.1 Uniform Etch Corrosion 1 -8

1.7.2 Galvanic Corrosion 1 -8

1.7.3 Pitting Corrosion 1 -9

1.7.4 Intergranular Corrosion 1-9

1.7.5 Exfoliation Corrosion 1-9

1.7.6 Concentration/Crevice Corrosion 1 -9

1.7.7 Stress Corrosion Cracking 1-11

1.7.8 Hydrogen Embrittlcment 1-11

1.7.9 Corrosion Fatigue 1-11

1.7.10 Filiform Corrosion 1-11

1.7.11 Fretting Corrosion 1-12

1.8 Metals Affected By Corrosion 1-13

1.8.1 Magnesium 1-13

1.8.2 Steel 1-13

1.8.3 Aluminum 1-13

1.8.4 Copper and Copper Alloys 1-13

1.8.5 Stainless Steel 1-13

1.8.6 Nickel and Chromium 1-14

2 CLEANING 2-1

2.1 General 2-1

2.1.1 Introduction 2-1

2.1.2 SE Wash Cycles 2-1

2.1.3 Definition of Cleaning 2-1

2.1.4 Types ofCleaners 2-1

2.1.5 Methods of Cleaning 2-1

2.1.6 Cleaning Materials 2-8

2.1.7 General Cleaning Material and

Processes 2-13

2.1.7.1 Cleaning Solutions 2-13

2.1.7.2 Cleaning Compounds 2-14

2.1.7.3 Water Temperature 2-14

2.1.7.4 Deployed/Remote Sites 2-14

2.1.7.4.1 Water Assessment 2-14

2.1.7.4.2 Engines and Engine Components 2-14

TABLE OF CONTENTS - CONTINUED

Chapter Page

2.1.8 Cleaning of Non-metal Parts Prior

to Painting 2-14

2.1.8.1 Composites 2-14

2.1.8.2 Plastics 2-14

2.1.9 Cleaning of Electrical Parts 2-14

2.1.10 Preparation of SE for Cleaning 2-15

2.1.11 Cleaning of Engine Components

and Enclosures 2-15

2.2 Mechanical Cleaning 2-16

2.2.1 General Information 2-16

2.2.2 Coating Removal on Composite

Surfaces 2-16

2.2.3 Coating Removal on Metallic

Surfaces 2-17

2.2.4 Grinding 2-17

2.2.5 Wire Brushing 2-17

PAINTING, SEALING. CORROSION PREVENTIVE

COMPOUND APPLICATION 3-

3.1 General 3-

3.2 Definition of Exposure 3-

3.3 Requirements For Painting - Field Level .3-

3.3.1 Complete Repainting Criteria 3-

3.3.2 Abrasive Blasting 3-

3.3.3 Temporary Coating Repairs 3-2

3.3.4 Touch-up Primer 3-2

3.4 Requirements For Painting - Depot

Level and Contractor Support 3-2

3.4.1 Corrosion Rework Determination 3-2

3.4.2 Contractor Compliance 3-2

3.5 Authorized Colors, SEMPENS, and

Materials 3-2

3.5.1 SE Standardized Colors 3-2

3.5.2 SE Standard Topcoat 3-3

3.5.3 Authorized Colors for Liquid Oxygen, Nitrogen Storage Carts and Tanks 3-4

3.5.4 Passenger or Loading Ramps 3-4

3.5.5 Presidential Support Equipment and

USAF Demo Team 3-4

3.6 Corrosion Treatment For Steel Cables 3-4

Chapter

3.

3.

3.

3.

8.1

8.2

3.8.3

3.

3.

3.

3.

3.

,9.1

9.2

.10

.10.1

.10.2

.11

.11.1

.11.2

.12

.12.1

3.12.2

3.13

3.13.1

3.13.2

3.13.3

3.13.4

3.13.5

3.13.6

3.14

3.15

3.16

3.16.1

Page

Piano Type Hinges 3-4

Mating Surfaces Protection

Requirements 3-4

Mating Surfaces - Bare Steel 3-4

Mating Surfaces - All Other Metals 3-4

Sealers and Sealant Usage 3-4

Acoustical Material Precautions 3-6

Coustifoam PUI and AF 3-6

Nonmetallic Fasteners 3-6

Drainage 3-6

Fluid Collection Points 3-6

Modifying Fluid Collection Points 3-6

Maintenance Stand Rails and Rail

Holders 3-7

Drain Holes 3-7

Drain Hole Corrosion Prevention and Treatment 3-7

Hollow Structural Members 3-7

Drainage for Closed Hollow

Members, When Open Drain Holes arc Possible 3-7

Drainage for Closed Hollow

Members, When Open Drain Holes arc Not Possible 3-7

Corrosion Preventive Compounds

(CPC).., 3-8

M1L-PRF-81309 3-8

MIL-DTL-85054 3-9

MIL-PRF-16173 CPC Solvent

Cutback, Cold Application 3-9

MIL-PRF-63460 Lubricant, Cleaner, and Preservative for Weapons and Weapon Systems 3-9

MIL-L-87177 Lubricants, Water

Displacing 3-9

CPC Methods of Application 3-9

CPC Application on Ferrous Alloys 3-9

CPC Application on Other Alloys 3-9

Coating Applications 3-10

Material Selection 3-10

/0\

Chapter Page

3.16.2 SE Surface Preparation Categories 3-12

3.16.3 Organic Zinc-Rich Primer 3-12

3.16.4 MIL-PRF-85285 Polyurethane, Type 1 3-13

3.16.5 Thermal Spray Coating Systems 3-13

3.17 Field Level Maintenance

Painting Requirements 3-15

3.17.1 Touch-Up Painting 3-15

3.18 Maintenance Painting 3-15

3.18.1 Maintenance Painting Restrictions 3-15

3.18.2 Prepackaged Coating Touchup Kits 3-16

3.18.3 Radiators Coatings 3-16

3.19 Liquid Oxygen and Liquid Nitrogen

Servicing Carts and Storage Tanks... 3-16

3.19.1 Authorized Materials for Liquid

Oxygen and Nitrogen Tanks 3-16

3.20 Walkways and Stepping Surface

Coatings 3-16

3.21 Colors for Waste Containers 3-16

3.22 SE Undercoating 3-16

3.22.1 SE Undercoating Considerations 3-17

3.23 Storage Compartments 3-17

3.24 Split Wheel Assemblies 3-17

3.24.1 Split Wheel Coating Requirements 3-17

3.25 Mufflers 3-17

3.26 Miscellaneous Cleaning, Scaling, and

CPC Requirements 3-18

3.26.1 Scaling of Addrcssograph or

Dash-A Plates 3-18

3.26.2 Electrical Hardware and Terminals 3-18

3.26.3 Light Assemblies 3-18

3.26.4 Internal Electrical Components:

Circuit Breakers, Relays, etc 3-18

3.26.5 Electrical Connectors 3-18

3.26.6 Switches 3-19

3.26.7 Wire Harness and Cables 3-19

3.26.8 Heli-Coil Insert Replacement 3-19

4 MARKING OF SUPPORT EQUIPMENT 4-1

4.1 General 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

Chapter Page

4.2.3 Product Identification 4-1

4.2.4 SE Reflectorization 4-2

4.3 Agency Identification Markings 4-2

4.3.1 Air Force Owned - Contractor

Operated Equipment 4-2

4.3.2 Mobilized Equipment 4-2

4.4 Informational Markings (Optional) 4-3

4.5 Color, Style and Size of Markings 4-3

4.5.1 Use of Reflective Tape, Dccals, and Vinyl Lettering 4-3

4.5.2 Field Numbers 4-4

4.5.3 USAF Legends 4-4

4.5.4 Color Numbers 4-4

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

4.8 Fuel Cell Repair SE Identification 4-5

5 CORROSION PREVENTION AND CONTROL OF

HUSH HOUSES 5-

5.1 Materials 5-

5.1.1 Fastener Replacement 5-

5.2 Repair 5-

5.2.1 Galvanized Steel 5-

5.2.2 Carbon Steel 5-

5.2.3 Stainless Steel 5-

5.2.3.1 Type 321 Stainless Steel 5-2

5.2.3.4 AISI 409 Stainless Steel 5-2

5.2.3.7 Sealing 5-2

5.3 Prctreatment Compounds 5-2

5.3.1 Rust Remover 81287 (Naval Jelly) 5-2

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

Change 3 iii

Chapter

5.5.1

5.5.2

5.6

5.6.1

5.7

5.7.1

5.7.2

Structural Corrosion Protection

Camouflage Requirements

Inorganic Zinc Primed Surfaces

Primer Requirements on the Door

Frame Beams, Support Beams, and Exhaust Tube

Galvanized Surfaces

Roof.

Walls and Doors

Page

5-3

5-3

5-3

... 5-3

5-4

5-4

5-4

Chapter

6.4.2

6.5

6.6

6.6.1

6.6.2

6.6.3

6.6.4

CORROSION PREVENTION AND CONTROL

OF NOISE SUPPRESSOR SYSTEMS (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

6.6.5

6.6.6

Page

Galvanized Steel 6-1

AISI409 Stainless Steel 6-1

Scaling 6-2

Primers 6-2

Organic Zinc-Rich Primers 6-2

MIL-PRF-23236, Type 1, Class 3 6-2

Heat Resistant Primer Brincr 2905 6-2

Heat Resistant Silicone Coating -

Briner 2986 6-2

High Temperature Resistant Silicone

Coating - Briner 4765 6-3

High Temperature Resistant Silicone

Coating Thurmalox 270-18 6-3

EQUIPMENT AND CONSUMABLE

MATERIALS USED FOR CORROSION

CONTROL A-t

A. 1 Equipment and Consumable Materials ...A-1

LIST OF ILLUSTRATIONS

Number Title Page

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

1-2 Corrosion Accelerated by Condensed

Moisture 1-5

1-3 Open Cell Foam and Resulting Corrosion 1 -6

1 -4 View of the Results of Microbial Induced

Corrosion 1-6

1-5 Example ofUniform Etch 1-8

1-6 Example of Galvanic Corrosion - Steel Hinge

Bolted to an Aluminum Door 1-9

1-7 Example of Pitting Corrosion 1-9

1 -8 Illustration ofan Intergranular Corrosion Cell.... I -10

1-9 Example of Exfoliation Corrosion 1-10

1 -10 Examples of Concentration/Crevice Corrosion... I -10

1-11 Illustration of a Typical Concentration

Corrosion Cell l-ll

1-12 Example of Filiform Corrosion 1-12

1-13 Illustration of a Fretting Corrosion Cell 1-12

3-1 Example of Standing Water Due to

Inadequate Drainage Provisions 3-6

Number Title Page

3-2 Hollow Member Drain Hole Configuration 3-7

3-3 Hollow Member Weld-Nut Configuration 3-8

3-4 Corrosion Under Data Plate 3-18

4-1 NATO Liquid Oxygen Servicing Markings 4-1

4-2 NATO Liquid Nitrogen Servicing Markings 4-1

4-3 Sample Mobility Placard 4-4

4-4 1,500 LB Utility Crane 4-7

4-5 ACE Air Conditioner MCI A, Diesel 4-9

4-6 AF/M27M-1 Pumping Unit, Hydraulic, Diesel Driven 4-11

4-7 AF/M32T-1 Cabin Leakage Tester 4-13

4-8 Aircraft Oxygen Servicing Cart 4-15

4-9 A/M24T-8 Load Bank 4-17

4-10 A/M32A-60A Gas Turbine Generator 4-19

4-11 A/M32A-86 Generator, Diesel 4-21

4-12 A/M32A-95 Compressor, Gas Turbine, Trailer Mounted 4-23

4-13 A/M32C-10C/10D Air Conditioner Set 4-25

4-14 A/M32C-5 Air Conditioner Set 4-27

4-15 Auxiliary Ground Power Unit (AGPU) 4-29 iv Change 3

LIST OF ILLUSTRATIONS - CONTINUED

<0\ jjw\

Number Title Page

4-16 B-l/B-2 Air Conditioner, Trailer Mounted 4-31

4-17 B-4 Maintenance Stand 4-33

4-18 B-5 Maintenance Stand 4-35

4-19 B-2 Maintenance Stand 4-37

4-20 B-7/B-1 Maintenance Stand 4-39

4-21 B809A Generator Set 4-41

4-22 C-l Maintenance Stand 4-43

4-23 Spraying Unit, Corrosion Control Wash Cart 4-45

4-24 Engine Oil Bowser 4-47

4-25 EPU-6 Aircraft Power Supply 4-49

4-26 FDECU-3 Environmental Control Unit 4-51

4-27 Fuel Bowser 400 Gallon 4-53

4-28 H-l Heater 4-55

4-29 HDU-13M Heater 4-57

4-30 Hydraulic Cart 4-59

4-31 Jack, Hydraulic 10-30 Ton 4-61

4-32 Jack, 35 Ton, Axle 4-63

4-33 Liquid Cooling Service (LCS) Cart 4-65

4-34 Liquid Oxygen Cart 4-67

4-35 LN2 Liquid Nitrogen Cart 4-69

LIST OF

Number Title Page

4-36 MC-1A High Pack Air Compressor 4-71

4-37 MA-3D Air Conditioner 4-73

4-38 MC-2A Air Compressor 4-75

4-39 MC-7 Air Compressor 4-77

4-40 MD-1 Towbar 4-79

4-41 MEP Generators 4-81

4-42 MHU-83C/E Bomblift Truck 4-83

4-43 MJ-1B Bomblift Truck 4-85

4-44 Hydraulic Test Stand 4-87

4-45 Light Cart, FL-ID 4-89

4-46 NF-2D Light Cart, Diesel 4-91

4-47 Oil Cart 4-93

4-48 Purging Unit GSU-62M LOX Storage 4-95

4-49 Radomc Dolly 4-97

4-50 Self-Generating Nitrogen Cart 4-99

4-51 Service Cart 4-101

4-52 Triclectron Generator 4-103

4-53 Universal Maintenance Stand 4-107

4-54 New Generation Heater 4-109

5-1 Angle Iron Sealant Application 5-2

TABLES

/f^\

Number Title Page

1-1 Galvanic Series of Metals and Alloys 1-3

1-2 Corrosion of Metals - Type of Attack and

Appearance of Corrosion Products 1-14

2-1 Wash Interval Based on Corrosion Severity

Zones 2-2

2-2 Authorized Cleaning Materials 2-10

3-1 Authorized Coating Systems 3-3

Number Title Page

3-2 Pretreatment Instructions 3-10

3-3 Metalization Material Sources of Supply 3-14

4-1 Mobility Placard Construction Information 4-3

4-2 Mobility Placard Stencil Requirements 4-3

5-1 Hush House Coating Chart 5-3

A-l Equipment and Consumable Materials List A-l

Change 3 v/(vi blank)

FOREWORD

^p

I

1. PURPOSE.

The purpose of this manual is to provide information necessary to prevent or minimize the impact of corrosion on Support

Equipment (SE). This manual is designed to provide basic cor rosion principal, theory, identification, prevention and control information to enable SE technicians to differentiate between the different types of corrosion in order to identify the appro priate temporary repair materials and processes. 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 Corro sion 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 guid ance for corrosion prevention and control activities of con tracted maintenance inspection, repair, and overhaul of SE. If conflicting instructions occur that pertain to the marking and painting of USAF SE, the end item manual takes precedence over this manual. Conflicts in resolving any conflicting materi als and processes application requirements shall be referred to the Air Force Corrosion Prevention and Control Office, AFRL/

MLS-OLR, Robins AFB, GA. Conflicts regarding all other cri teria in this manual shall be referred to WR-ALC, Robins AFB, GA for resolution.

2.1 Chapter 1 Description. This chapter provides the basic

information needed by SE technicians to accurately identify 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 rec ommended SE wash cycles based on location; provides a list ing 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, scaling requirements, and corrosion preventive com pound 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 materi

als and processes for construction and maintenance of Hush

Houses.

2.6 Chapter 6 Description. This chapter covers the materi

als and processes forNSS.

2.7 Appendix A Description. This appendix provides a list

of consumable material authorized for use on SE.

3. ABBREVIATIONS AND ACRONYMS.

Abbreviations and acronyms used in this manual arc in the accordance with ASME Y 14.38.

Abbreviation

AISI

AFRL/MLS-OLR

BBE

BOD

CPC

CRES

DO

ESD

ID

MSDS

MWAS

NACE

OD

Definition

American Iron and Steel Institute

Air Force Corrosion Prevention and Control Office

Base Biocnvironmental Engineer

Biochemical Oxygen Demand

Corrosion Preventive Compound

Corrosion Resistant Steel

Dissolved Oxygen

Electrostatic Discharge

Inside Diameter

Material Safety Data Sheet

Metallization Process Metal Wire

Arc Spray

National Association of Corrosion

Engineers

Outside Diameter

Occupational Safety and Health

Administration

PH

PSI

PSIG

PM

PPE

QPL

RH

RTV

Potential of Hydrogen

Pounds Per Square Inch

Pounds Per Square Inch Gauge

Preventive Maintenance

Personal Protective Equipment

Qualified Product List

Relative Humidity

Room Temperature Vulcanizing

Change 3 vii

Abbreviation

SCC

SE

SSDC

TDS

Definition

Stress corrosion cracking

Support Equipment

Steel Structure Painting Council

Total Dissolved Solids

4. LIST OF RELATED PUBIICATIONR

Below is a list of publications referenced in this manual.

Number Title

TO 00-25-234 General Shop Practice Requirement for the Repair, Maintenance and Test of

Electrical Equipment

TO 00-35D-54 USAF Materiel Deficiency Reporting and Investigating System

TO 00-5-1 Air Force Technical Order Systems

Number Title

TO 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, Aerospace and

Non-Aerospace Equipment

TO 35C2-3-1 - Periodic Inspection Work Cards -

426WC-4-20-1 Diesel Engine Driven Generator Sets

A/M32A-86 Series

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

TO 42B-1 -23 Management of Recoverable and

Waste Liquid Petroleum Products

5. RECOMMENDATIONS FOR CHANGES

Recommendations for changes shall be submitted on AFTO

Form 22 in accordance with TO 00-5-1.

viii

SAFETY SUMMARY

/0

/fl

1. GENERAL SAFETY INSTRUCTIONS.

The safety precautions in AFOSH Standard 91-66, AFOSH

Standard 91-100 and OSHA Standard 1910.107 are applicable to the operation of paint shops and spray-painting equipment and shall be followed during cleaning and repainting of SE.

2. WARNING AND CAUTION STATEMENTS.

These statements have been strategically placed throughout this text prior to operating or maintenance procedures, prac tices or conditions considered essential to the protection ofper sonnel (WARNING) or equipment and property (CAUTION).

A WARNING and CAUTION will apply each time the related step is repeated. Prior to starting any task, the WARNINGS or

CAUTIONS included in the text for the task will be reviewed and understood.

3. DEFINITIONS.

The following definitions apply to WARNINGS and CAU

TIONS found throughout this publication.

WARNING

Highlights an operation or maintenance procedure, practice, statement, etc., which, if not strictly ob served, could result in injury, long term health hazard or death to personnel.

I CAUTiofi i

Highlights an operation or maintenance procedure, practice, statement, etc., which, if not strictly ob served, could result in damage or destruction to equipment or loss of mission effectiveness.

NOTE

Highlights an essential operating or maintenance pro cedure, condition or statement.

4. MATERIALS HANDLING.

4.1 Personnel Hazards. Many of the materials and proce

dures outlined in this technical order are potentially hazardous to personnel, if used improperly. When using chemicals such as paint strippers, cleaning compounds, conversion coatings, and solvents, follow the correct procedures and wear appropri ate protective gear to prevent injury to personnel. Read the appropriate Material Safety Data Sheet (MSDS), manufac turer'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 cor rosion. Refer to DOD 6050.5-LR, Hazardous Material Infor mation System, FED STD 313, Material Safety Data, Transportation Data, and Disposal Data for Hazardous Mate rial Furnished to Government Activities, or the appropriate systems command documents for the handling, storage, and disposal of hazardous materials. When in doubt, contact the local safety office, base bioenvironmcntal office, or regional medical center for guidance.

4.2 Environmental Hazards. Many of the materials and

procedures outlined in this technical order are also potentially hazardous to the environment. Wherever possible, methods for preventing pollution, minimizing waste, and using less toxic materials are given. Consult the base bioenvironmcntal office for information about the handling, storage, and disposal of hazardous waste.

5. 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 precautions and instructions people must understand and apply during many phases of operation and maintenance to ensure personal safety and health and the protection of Air Force property.

5.1 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 remove power, discharge, and ground a circuit before touching it.

Adhere to all lock out/tag out requirements.

5.2 Resuscitation. Personnel working with or near danger

ous voltage shall be trained in modem methods of resuscita tion. Information and training sources may be obtained from the Director of Base Medical Services.

5.3 Finger Rinqs/Jewelrv. Finger rings have caused many

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

5.4 Compressed Air. Use of compressed air can create an

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

5.5 Dangerous Pressures. Care must be taken during test

ing 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.

6. PERSONAL PROTECTIVE EQUIPMENT fPPEL

Ifunique local conditions make compliance with the protective clothing or other occupational health requirements specified in this manual unnecessary or impractical, obtain an evaluation of the operation from the Biocnvironmental Engineer. The Bioen-vironmental Engineer or Base Safety Office will determine the required precautions and approved PPE.

7. CLEANERS/CHEMICALS/PAINTS/PRIMERS.

Some cleaners, chemicals, paints, and primers have adverse effects on skin, eyes, and the respiratory tract. Observe manu facturer's warning labels. Material Safety Data Sheet (MSDS) and other instructions for proper handling, storage, and dis posal; and current safety directives. Use only in authorized areas.

8. ELECTROSTATIC DISCHARGE (ESDI

Certain circuit card assemblies and their components will be damaged by seemingly undetectablc 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 DOD-HNBK-263, Electrostatic Discharge Control

Handbook for Protection of Electrical and Electronic Parts, Assemblies and Equipment.

%i.

CHAPTER 1

CORROSION THEORY, IDENTIFICATION, CAUSES AND EFFECTS

ff

1.1 PURPOSE.

The purpose of this chapter is to provide SE maintenance personnel with the basic knowledge necessary 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 under stand corrosion causes and effects and be able to recognize there are several types of corrosion with different preventive measures. This chapter is an introduction to corrosion theory, the causes of corrosion and the factors that influence its development. The various forms ofcorrosion 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 because of its chemical reaction with the surrounding envi ronment. 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, condensation, 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 aluminum, magnesium, iron, nickel, titanium, cadmium, chromium, copper, and carbon) and non-metals (such as hydrogen, 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.

Electrons also flow through water solutions, but only in the presence of ions.

1.3.3 Ions. Atoms or groups of atoms bound together

that is either positively or negatively charged. An electrical current occurs when ions are forced to move through water solutions. 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 corrodes, 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, hy droxides, and sulfides. Four conditions must exist before this type of corrosion 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

cathode) that has less of a tendency to corrode than the anode must be present. Examples include a different metal, a protected part of the same metal, or conductive plastics/ composite.

1.4.3 Electrolyte. A conductive liquid (electrolyte) must

connect the anode and cathode so that ions can carry electrical current between them.

1.4.4 Electrical Path. Electrical contact between the

anode and cathode (usually in the form of metal-to-metal contact) 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 connect ing 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.

1.5 DEVELOPMENT OF CORROSION.

1.5.1 Corrosion Origination Locations. All corrosive

attacks 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 penetrate into and through the metal. When corrosion prod ucts 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.

1-1

ELECTROLYTE

[FRESH OR SALTWATER,

ACIDS. GASES, ETC.)

METAL

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

1.5.2 Corrosion Under Painted Surfaces, ['aim coal

ings can mask the initial stages of corrosion. Because corrosion products occupy more volume than tlie original metal, rrcquenily inspect paint surfaces for irregularities such as blisters, flakes, chips, and lumps.

1.6 FACTORS INFLUENCING CORROSION.

Both natural and man-made environments cause corrosion of

SE. Natural conditions thai affect lite corrosion process are moisture, temperature, salt atmospheres, ozone, sand, dust, solar radiation, insects and birds, and microorganisms. Man-made conditions that aflfeci the corrosion process arc Indus trial pollution, manufacturing operations, storage conditions, and Shipment. By understanding these conditions, mainte nance personnel will he better able to prevent SE damage.

Factors that Influence metal corrosion and die rate at which it occurs arc outlined below.

1-2

Table 1-1. Galvanic Series of Metals and Alloys

ANODIC (HIGH CORROSION POTENTIAL)

MAGNESIUM ALLOYS

ZINC (PLATE)

BERYLLIUM

BERYLLIUM (PLATE)

URANIUM (DEPLETED)

ALUMINUM ALLOYS

INDIUM

TIN (PLATE)

STAINLESS STEEL 43O (ACTIVE)

LEAD

1010 STEEL

CAST IRON

STAINLESS STEEL 410 (ACTIVE)

COPPER (PLATE)

NICKEL (PLATE)

AM 350 (ACTIVE)

CHRONIUM (PLATE)

STAINLESS STEELS 35O. 310. 301. 304 (ACTIVE)

STAINLESS STEELS 43O. 410 (PASSIVE)

STAINLESS STEELS 13-8, 17-7 pH (ACTIVE)

[ BRASS.YELLOW. NAVAL

[ STAINLESS STEEL 316L (ACTIVE)

BRONZE 22O

COPPER

STAINLESS STEEL 347 (ACTIVE)

COPPER-NICKEL 715

STAINLESS STEEL 202 (ACTIVE)

MONEL400

STAINLESS STEEL 2O1 (ACTIVE)

STAINLESS STEEL 321, 316 (ACTIVE)

STAINLESS STEEL 3O9. 13-8.17-7 pH (PASSIVE)

STAINLESS STEEL 3O4. 3O1. 321 (PASSIVE)

STAINLESS STEEL 201. 316L (PASSIVE)

STAINLESS STEEL 286 (ACTIVE)

AM355 (ACTIVE)

STAINLESS STEEL 202 (PASSIVE)

CARPENTER 20 (PASSIVE)

AM355 (PASSIVE)

TITANIUM ALLOYS

SILVER

PALLADIUM

GOLD

RHODIUM

PLATINUM

CARBON/GRAPHITE

CATHODIC (LOW CORROSION POTENTIAL.)

1-3

1.6.3 Anode and Cathode Surface Area. The rate of gal

vanic corrosion also depends on the size of the parts in con tact. If the surface area of the corroding metal (the anode) is smaller than the surface area of the less active metal (the cath ode), corrosion will be rapid and severe. However, if the cor roding metal is larger than the less active metal, corrosion will be slow and superficial. For example, an aluminum fastener in contact with a relatively nonreactivc Moncl structure may cor rode severely, while a Moncl bracket secured to a large alumi num member would result in a relatively 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 tem perature environments tend to produce more rapid corrosion 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. Corro sion does not occur in very dry conditions. For this reason, desiccants or dehumidification systems arc placed in, or con nected to shipping or storage containers to create very dry local environments. The equipment's proposed operational 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 scaled components. Typically, desert condi tions arc thought to have low humidity and rainfall. However, there are areas of the world considered as desert with high daytime temperatures, moderate to low night time tempera tures, high humidity (in areas such as the Persian Gulf), ultra violet 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 °F to +59 °F (-32 °C to +15 °C) in the winter and from +59 °F to +125 °F (+15 °C to +52 °C) in the sum mer. The relative humidity (RH) also fluctuates between five and 100%. The most critical areas 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 concentra tions 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 tem peratures, the temperate zone is also the most heavily popu lated. Consequently the smoke, smog, ozone, and corrosive fumes associated with heavy industry are also found there.

1.6.4.3 Tropics. One of the greatest challenges to SE manu

facturing 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 the stand point 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 corrosion. When high humidity and temperature conditions are combined with salt-laden air, the corrosive environment becomes extremely severe. The critical combination of high temperatures, conden sation, high relative humidity, and contaminants such as salt and sand may cause premature structural failure of equipment due to corrosion. Deterioration of the materials used in elec tronic equipment may also be accelerated. Thin film corrosion on electrical contact points and pins act as insulators to electri cal current adversely affecting the operations of SE.

1.6.4.3.1 Factors of Influence in Tropical Environ

ments. Tropical environments arc noted for long periods of heavy rainfall, during which 100 inches or more of rain may fall. Extended periods of high heat and humidity contribute 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 protective contain ers/measures and frequent preventive maintenance. Microor ganisms multiply excessively in tropical environments and attack many non-metallic materials. Many items become cov ered with fungi in a matter of hours. Electronic equipment requires special efforts for effective operation in the tropics.

Intensive preventive maintenance and the best possible protec tive techniques are necessary for SE and their components in tropical environments.

1.6.5 Heat Treatment and Grain Direction. When heat-

treated, heavy sections of metals do not cool uniformly because the metallic grain/crystalline structures tend to vary in chemical composition from one part of the metal to another.

This can cause galvanic corrosion if the metal crystals are more active than another or contain contaminates. Alloys that are fabricated by rolling, extruding, forging, or pressing have properties that depend highly on the metal grain/crystal direc tion (parallel to grain elongation vs. cross grain). For example, exposed end grain corrodes much more easily than flattened elongated surfaces in sheet stock. This explains why exfolia tion occurs at the structural edges or next to countersunk fas teners on certain types of alloys.

1.6.6 Electrolytes. Electrically conducting solutions are

easily formed on metallic surfaces when condensation, salt spray, rain, or rinse water accumulate. Dirt, salt, and carbon deposits from engine exhaust and engine exhaust gases can combine with water on wet surfaces thereby increasing the electrical conductivity of the electrolyte and the rate of corro-

1-4 operation in the iropics. Intensive preventive maintenance and the besi possible protective techniques are necessary for

SE and their components in tropical environments.

1.6.5 Heal Treatment and Grain Direclion. When

heat-treated, heavy sections of meials do nol cool uniformly because tlie metallic grain/crystalline struciures tend lo vary in chemical composition from one part of the metal to another. This can cause galvanic corrosion if the metal crystals arc more active than another or contain contaminates.

Alloys that arc fabricated by rolling, extruding, forging, or

[trussing have properties that depend highly on the metal grain/crystal direction (parallel to grain elongation vs. cross grain). For example, exposed end grain corrodes much more easily than tlatiened elongaled surfaces in sheet slock. This explains why exfoliation occurs at the structural edges or next to countersunk fasteners on certain types of alloys.

1.6.6 Electrolytes, lilectrically conducting solutions are

easily formed on metallic surfaces when condensation, salt spray, rain, or rinse water accumulate. Din. salt, and carbon deposits from engine exhaust and engine exhaust gases can combine with water on wet surfaces (hereby increasing ihe elecirica! conductivity of ihe electrolyle and tlie rate of corrosion. Improper dilution of cleaning chemicals, combin ing cleaning compounds togeihcr, or ihe use of unauthorized cleaning material can cause the cleaning solution lo become an electrolyte.

1.6.6.1 Moisture is present in air as a gas (water vapor) or

as finely divided droplets of liquid (mist or log) and often contains contaminants (such as chlorides, sulfates. and ni trates) (hat increase its corrosive eilecis. Moisture will enter all areas of SE that air can enter. All enclosed areas, that are not hermetically sealed, will allow air to enter and leave as

(he difference in pressure between ihe inside and outside tlie equipmeni changes. These pressure differences occur when atmospheric pressure changes and when ihe air temperature inside an enclosed area changes. As the surrounding surfaces are healed, moislure-laden air is drawn into the enclosed area or absorbed in open eel! foam. As the air around the equipment cool, moisiure will condense in the enclosed areas and settle in (he lowest area of ihe part. 'Hie enclosed areas are often hidden and/or inaccessible. Moisture is difficult to remove and llie subsequent corrosion may be dillicull lo identify in ihe early stages.

1.6.6.2 Sail laden atmospheres pose a continual problem

in locations operating near coasial environments. When dissolved in water, sail solutions form very effective eleciro-lytes. The ocean, which is 3.5% to 3,9% salt, is ihe world's primary source of salt. Normal sea winds carry from 10 to

100 lbs of sea salt per cubic mile of air. ISases located close to marine environments are continually exposed to the sail laden atmosphere. Because dissolved sails are sirong electro lytes, it is easy to understand why coastal environments are listed in the moderate to severe corrosion prone categories and require frequent rinsing and cleaning to remove the salt deposils. Regular use of chloride removal materials as listed in Appendix A is recommended for equipment operating in areas with high concentrations of salt.

Figure 1-2. Corrosion Accelerated by Condensed Moisture

1.6.6.3 Condensed moisture will usually evaporate as the

surrounding air warms but will leave behind its contaminants

(residues), including salts. This can result in the build-up of soils and sail contamination. Salt-laden condensation may collect at the lowest surface of the equipment. The lowest surfaces are usually the last to dry. As the condensation continues lo collect at the lowest surfaces the contaminates/ electrolytes become more concentrated. Dried salt deposits can be difficult to remove without the use of chloride dissolving malerials listed in Appendix A. Condensed mois ture and its contaminants can also be trapped in close fitting, wettable joints, such as faying surfaces. Some gasket and packing malerials will absorb several times their weight in water and, when heated, can transmit this retained moisiure into the sealed area. Moisture can accumulate in such areas through successive cycles of warming and cooling and cause corrosion on the interior of (he part resulting in premature structural failure as shown in Figure 1-2.

1-5

Figure 1-3. Open Cell I and Resulting Corrosion

1.6.6.4 Open cell foam, see Figure 1-3, is a sponge-like

material used mainly for sound suppression and insulation.

Humidity, condensation, rainfall, etc., is absorbed into the foam and ultimately migrates to the mating metal surface to which it is attacticd. The absorbed moisture is very slow in drying out and provides the moisture/elecirolyte against the meial surfaces. When possible, open cell foam should not be used. Closed cell types of foam may be suitable subsiitutes for this material and will not absorb moisiure. If open cell foam is the only material suitable for your needs, prior to installation in the SH, seal all open cell surfaces and sides of any perforations in the foam with a polysullide type sealant such as MIL-PRF-X1 733. Sealing any tears in the foam or any unsealed sides and edges of the foam will preclude any fluid absorption by the foam.

1.6.6.5 Airborne industrial pollutants also contribute to the deterioration of nonmeiallie materials and severe corrosion of metals. Hie most aggressive are: carbon (from Internal combustion engine exhaust), nitrates (from agricultural fer tilizers), ozone (from electrical motors and welding opera tions), sulfur dioxide (from engine exhaust and industrial and ship smoke stacks), and sulfates (from automobile exhaust),

1.6.6.6 .Sand, dust, and volcanic ash are present in many areas, but particularly in industrial areas where they often contain a number of tar products, ashes, ami soot. Dust is also found in tropical /ones with plentiful rainfall and arid zones where there is little or no rainfall. Sand and dust are extreme problems in deserts because the wind carries dry. powdery sand and dust. During sandstorms, sand and dust can pen etrate sealed equipment and many internal areas of SB. Sand, dust, and volcanic ash are hygroscopic and can absorb and hold moisture when present on internal or external surfaces of

SE or electronic parts. Dusi from volcanic areas contains chlorides and sulfates, dusl from desert areas may contain chlorides, carbonates, and sulfates. These materials are ex tremely corrosive in the presence of moisture. Aldiough small amounts of sand or dust may be unnoticed by operating personnel, ihey may be sufficient to initiate and accelerate corrosion.

1.6.7 Microbial Induced/Influenced Corrosion, though rarely seen

Al-on SE, microbial induced/influenced corrosion, as the term is used in this manual, includes the aggressive action of bacteria, fungi, or molds that can be found on SE Microorganisms are nearly everywhere and oulnumber all other types of living organisms. 'ITiose organ isms causing the greatest corrosion problems are bacteria and fungi. Damage resulting from mierobial growth can result from: (11 the tendency of (he growth to hold moisture which then causes corrosion; (2) digestion of the substrate as food for the microorganism; or (3) corrosion of the surface beneath die growth by secreted corrosive fluids of die action of bacteria, fungi, or molds on a metal surface, see Figure 1-4.

1.6.7.1 Bacteria may be either aerobic or anaerobic.

Aerobic bacteria require oxygen to live. They can accelerate corrosion hy oxidizing sulfur to produce sulfuric acid or by oxidizing ammonia to produce nitric acid. Bacteria living adjacent to metals may promote corrosion by depleting the oxygen Supply or by releasing metabolic products. Anaerobic bacteria, on the other hand, can survive only when free oxygen is not present. 'Hie metabolism of these bacteria requires them to obtain food sources by oxidizing inorganic compounds such as iron, sulfur, hydrogen, and carbon mon oxide. The resultant chemical reactions cause corrosion.

1 .G.7.2 Microbial attack can be prevented by frequent and thorough cleaning of the affected areas and applying moisture-proofing coalings to nutrient materials or by drying the interiors of compartments w:ilh desiccants. However, some moisture-proofing coatings are attacked by microorgan isms, especially if they are used on contaminated surfaces.

1-6 r

Figure 1-4. View of Hie Results of Mfcrobial In duced Corrosion

1.6.7.3 When dry. some microorganisms can survive in

spore form for long periods and can become active when moisture is available. When desiccanis become saturated and unable to absorb the moisture passing Into ihe affected area, microorganisms can begin to grow. Dirt, dusi, and other airborne contaminants are ilie least recognized contributors to microbial attack. Unnoticed, small amounts of airborne debris may be sufficient to promote fungal growth.

1.6.8 Mechanical Stress. Manufacturing processes

Such as machining, forming, welding, or heat treatment can leave stresses in SE pans. Almost all alloys in SH construc tion are sensitive to a form of corrosion known as stress corrosion cracking. Iliis residual stress causes corrosion to proceed more rapidly in structurally important regions of the part until failure occurs.

1.6.9 Time. As time goes on, metals naturally lend to

corrode. In some cases, die corrosion process occurs at the same rate, no mailer how long the metal has been exposed to the environment In other cases, corrosion can decrease with lime (because of the barrier formed by corrosion products) or increase (if a barrier to corrosion is being broken down).

1.6.10 Manufacturing. During the manufacture, assem

bly, or repair of SE. many factors can cause the introduction of corrosion. Use of unsuitable materials and improper materials processing can cause corrosion. Shearing or hole-punching operations on some melal alloys, especially on high-strength aluminum, may create stresses thai will lead to corrosion or provide a slight lip lo inhibit complete drainage from an area. Raised edges of the hole-punching operations may eause incomplete drainage of electrolytes once the panels arc installed. Assembly of parts in areas contaminated by fumes or vapors from adjacent operations may entrap fumes in llie equipment, which mighl lead to future corrosion.

Areas without humidity control may be sources of condensed moisture. Inadequate or non existent sealant usage, improper material selection, use of open cell foam for sound suppres sion are other causes that contribute lo premature structural failure of SH.

1.6.11 Storage. Hven traces of corrosive vapor in pack

ages containing SE parts may result in serious corrosion.

Moreover, liie natural "brealhing" of packages may introduce moisture inio parts and equipment. Decomposed packing materials can emit corrosive vapors during prolonged storage, which can create serious corrosion of equipment and the parts stored in these packages.

1.6.12 Degradation of Non-metals. Nonmetallic ma

terials (plastics, elastomers, paints, and adhesives) are not subjeel lo electrochemical corrosion because ions are not easily formed from nonmelallic elements and ihe electrical conduciivity of non-metals is extremely low. The degradation of non-metals depends on Hie chemical make-up of the material and the nature of the environment. In general, nonmelallic materials used on equipment are selected for their performance properties (flexibility, transparency, sircngth. electrical resistance, etc.) and their resistance to heat, impact, abrasion, ultraviolet radiation, moisture, ozone and oilier detrimental gases, and operational fluids (such as hydraulic fluid, lube oil. cleaners, deicing lluids, etc.). How ever, the use of unauthorized maintenance chemicals and procedures can accelerate degradation and ultimately lead to material failure resulting in leakage, corrosion, electrical shorts, crazing, and/or mechanical failure.

1.6.13 Preventive Maintenance (PM). I'M is probably

one of the easiest, most elTeciive, and least expensive means of preventing corrosion and is ihe process organization maintenance personnel can control. Each type of corrosion has its own peculiarities and will require special treatment.

However, there is a common four point approach in devel oping an effective corrosion prevention and control program.

The four point approach consists of (1.) the early identifica tion of corrosion, (2.) the early and thorough removal of corrosion and proper treatment of ihe corroded area (3.) ihe complete removal of electrolytes through frequent cleaning with approved, properly mixed cleaning compounds, (4.) and the application and maintenance upkeep of effective protec tive coalings.

1.6.13.1 Corrosion can be minimized by frequent washing

because the extent of corrosion depends on the length of time electrolytes ;ire in contact with metals. If Qualilied Product

List (QP1.) approved cleaners and addilives arc used, fre quently cleaning of equipment based or operating in a…