WFIRST-IC-SPEC-0062_-.pdf

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National Aeronautics and Space Administration

Goddard Space Flight Center Greenbelt, Maryland

WFIRST-IC-SPEC-0062, Revision -

Wide Field Infrared Survey Telescope (WFIRST), Code 448

Process Requirements for Application of BR127 Primer, Instrument Carrier (IC)

GSFC WFIRST CMO

July 10, 2019

Released

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Requirements for Application of BR127 Primer WFIRST-IC-SPEC-0062, Revision -ii

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Process Requirements for Application of BR127 primer, Instrument Carrier (IC)

Review/Signature/Approval Page

Prepared by:

Wes Alexander

Approving Signature Authority:

Wes Alexander

Electronic Approval available on-line at: https://ipdtdms.gsfc.nasa.gov iii

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Preface This document is a Wide Field Infrared Survey Telescope (WFIRST) Configuration Management (CM)-controlled document. Changes to this document require prior approval of the applicable Signature Authority or designee. Proposed changes shall be submitted to the WFIRST CM Office (CMO), along with supportive material justifying the proposed change.

In this document, a requirement is identified by “shall,” a good practice by “should,” permission by “may” or “can,” expectation by “will,” and descriptive material by “is.”

Questions or comments concerning this document should be addressed to:

WFIRST Configuration Management Office Mail Stop 448 Goddard Space Flight Center Greenbelt, Maryland 20771 iv

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Change History Log

Revision Effective Date Description of Changes (Reference the Signature Authority Approval Date)

Revision - July 9, 2019 This was approved by the WFIRST Signature Authority via WFIRST-SCoRe-0186 on the effective date shown.

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Table of TBDs/TBRs/TBSs [optional]

Item No. Location Summary Individual/ Organization

Actionee

Due Date vi

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Table of Contents

1 INTRODUCTION

1.1 Purpose

1.2 Scope

1.3 Related Documentation

1.3.1 Applicable Documents [and Forms]

1.3.2 Reference Documents

2 REQUIREMENTS

2.1 General

2.1.1 Facilities

2.1.2 Safety

2.1.3 Equipment

2.1.4 Process Control

2.1.4.1 Monitoring of solutions

2.1.4.2 Single Lap Shear Test Specimens

2.1.4.3 Process Control Witness Coupon

2.1.4.4 Process Approval

2.2 Surface Preparation of Parts- General

2.2.1 General

2.2.2 Racking and Hanging of Parts

2.2.3 Part Handling

2.2.4 Cleaning of Parts after Etching

2.2.5 Initial Cleaning of all Metallic Alloys

2.2.6 Grit Blasting for Metallic Parts

2.2.6.1 Dry Grit Blasting

2.2.6.2 Cleaning Following Post Grit Blasting

2.3 Surface Preparation for Priming – Aluminum Alloys

2.3.1 Sodium Dichromate Acid Etch Process

2.3.1.1 Sodium Dichromate Acid Etch Solution

2.3.1.2 Procedure for Sodium Dichromate Acid Etch

2.3.2 Procedure for Phosphoric Acid Anodize (PAA)

2.3.3 Alternate methods for surface preparation of aluminum alloys

2.4 Surface Preparation for Priming - Titanium and Titanium Alloys

2.4.1 Removal of Re-cast Layer for Titanium Parts Machined by EDM

2.4.2 Nitric Acid/Ammonium Bi-fluoride Acid Etch Solution for Titanium Alloys

2.4.3 Procedure for Etching of Titanium and Titanium Alloys

2.4.4 Alternative Methods of Surface Preparation

2.5 Surface Preparation of Invar Alloys

2.5.1 Etching of Invar

2.5.1.1 Composition of etching solution shall be as follows

2.5.1.2 Procedure for Etching of Invar

2.5.2 Alternative surface preparation for Invar

2.6 Bake-out (Drying) Prior to Priming

2.6.1 Inspection

2.6.2 Spots

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2.6.3 Bake-out

2.7 Surface Exposure Time

2.8 Primer Application

2.8.1 Preparation of BR127 Primer

2.8.2 Primer Application

2.8.3 Primer Elevated Temperature Cure

2.9 Post Process Inspections

2.9.1 Visual Appearance

2.9.2 Primer Thickness

2.9.3 Primer Color

2.9.4 Acetone Wipe Testing

2.9.5 Primer Adhesion

2.9.6 Single Lap Shear Strength

2.10 Rework of Damaged Primed Areas

2.11 Storage

3 QUALITY ASSURANCE PROVISIONS AND TEST METHODS

3.1 General

3.2 Reference Standard for Visual Inspection

3.3 Appearance

3.4 Primer Thickness Test Method

3.5 Acetone Wipe Test Method

3.6 Adhesion Test Method

3.7 Single Lap Shear Testing

4 NOTES

4.1 Intended use

4.2 Typical Drawing Callout

4.3 Preparation for Bonding to Primed Surfaces

4.4 Suggested Source of Supply

APPENDIX A ABBREVIATIONS AND ACRONYMS

List of Figures Figure 1. Process Flow Diagram

List of Tables Table 1. Surface Exposure Time Table 2. Lap Shear Strength Requirements

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1 INTRODUCTION

1.1 Purpose

This specification covers performance measures for application of BR-127 primer for bonding of composite structures for the Wide Field Infrared Survey Telescope (WFIRST). The Contractor is responsible for compliance with all requirements within this specification.

1.2 Scope

This specification describes the process requirements and sets limits of acceptance for the surface preparation and application of BR127 Primer (Cytec Corporation) for the Instrument Carrier structure. This specification covers process requirements for aluminum, titanium and Invar.

1.3 Related Documentation

The latest versions of all documents below should be used. WFIRST documents can be obtained from URL: https://ipdtdms.gsfc.nasa.gov.

1.3.1 Applicable Documents [and Forms]

The following documents and drawings in effect on the day this specification was signed shall apply to the priming process. In the event of conflict between this specification and any referenced document, this specification will govern. In the event of a conflict between this specification and the engineering drawing, the requirements of the engineering drawing shall prevail.

Document Number Title IEST-STD-CC1246E Product Cleanliness Levels And Contamination Control

Program WFIRST-SYS-PLAN-0051 WFIRST Contamination Control Plan WFIRST-IC-SPEC-0046 Instrument Carrier Flight Structures Specification

1.3.2 Reference Documents

The following documents are referenced herein and amplify or clarify the information presented in this document. These documents are not binding on the content of this document.

Document Number

Title

ASTM D 1002 Standard Test Method for Apparent Shear Strength of Single Lap-Joint Adhesive Bonded Metal specimens by Tension Loading

ASTM D 2651 Standard Guide for preparation of Metal Surfaces for Adhesive Bonding ASTM D 2674 Standard Methods of Analysis of Sulfochromate Etch Solution Used in

Surface Preparation of Aluminum ASTM D 3933 Preparation of Aluminum Surfaces for Structural Adhesives Bonding

(Phosphoric acid anodizing) ASTM D 3359 Standard Test Methods for Measuring Adhesive by Tape Test SAE AMS 2488A Anodic Treatment- Titanium And Titanium Alloys, Solution PH13 Or

Higher

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2 REQUIREMENTS

2.1 General

The process for application of BR127 primer shall follow the flow diagram shown for reference in Figure 1.

Unless otherwise specified on the engineering drawing, parts processed per this specification shall meet the dimensions specified on the engineering drawing after application of primer. Parts may be etched more than one time, provided that the additional etching does not compromise the dimensions specified on the engineering drawing.

The processes used to prepare the surfaces and critical parameters, such as etch times, cure times, and material traceability, shall be recorded on the manufacturing traveler or certification log.

The use of processing fluids, including cleaning or etching fluids that contain free or ionic halogens is prohibited. Fluids which contain chlorine, bromine, fluorine, or iodine are specifically prohibited. This is due to the possibility of introducing stress corrosion cracking during processing of titanium alloys.

2.1.1 Facilities

Surface preparation, etching, and application of primer shall be performed in a clean, well ventilated area. There shall be no contamination sources in the area or via the ventilation system.

Doors and windows shall be kept closed to exclude dust and dirt.

2.1.2 Safety

Refer to safety data sheets for all critical information when handling chemicals. Necessary precautions shall be taken to protect skin, and eyes. Proper ventilation should be in place and utilized when performing etching, and priming operations. Respirators are required during priming operations

2.1.3 Equipment

Paint spray gun shall be equipped with an agitator.

All paint gun supply lines shall be kept free from condensation of oil and water by blowing out the lines as necessary. An air supply of 50-90 psi with a regulator and moisture trap is required.

It is recommended that the supply for paint guns have an inline moisture dryer or that bottled clean air or dry nitrogen be used as a supply for paint guns.

Wipes used shall be lint-free non-contaminating wipes including extracted wipers, or Texwipe 609 or equivalent.

Gloves used shall be non-contaminating, polypropylene or other approved material.

Brushes shall be non-lint producing.

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2.1.4 Process Control

2.1.4.1 Monitoring of solutions

Cleaning, etching, rinsing, anodizing and surface treatment solutions shall be monitored on a periodic basis. Solution concentrations shall be as specified herein or in the referenced specifications. Adjustments shall be made as necessary to maintain the concentration limits specified herein or in the referenced specifications. A logbook shall be maintained to record solution condition and actions taken to maintain the solution. Procured premixed materials shall be within manufacturer shelf life prior to use.

2.1.4.2 Single Lap Shear Test Specimens

A set of single lap shear specimens, minimum quantity of 5, shall be prepared along with the parts being processed to verify adequate surface preparation. These specimens shall be fabricated with the same materials (i.e. metal alloy) and under the same conditions as the parts being processed. Specific requirements for the lap shear configuration will be defined by GSFC.

2.1.4.3 Process Control Witness Coupon

A witness coupon shall be prepared along with the parts being processed to verify adequate surface preparation. This coupon shall be fabricated with the same materials (i.e. metal alloy) and processed under the same conditions as the parts being processed.

The witness coupon shall be prepared with primer applied to a portion of the coupon (approximately ½ of the coupon) to facilitate thickness testing per 3.4.

This witness coupon may be a separate coupon, or a single lap shear specimen may be used, provided the required testing does not compromise the use of the specimen for a single lap shear test.

2.1.4.4 Process Approval

Unless already approved by the MEB based on prior experience, the surface preparation and priming process shall be approved based one of the following:

a) Presentation of test data demonstrating compliance with the requirements of this specification, and confirmation of consistency of the priming process for the samples associated with the presented data and the process to be used for WFIRST hardware.

b) Processing of trial parts meeting the requirements of this specification, including the single lap shear strength requirements of paragraph 2.1.4.2.

Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

Figure 1. Process Flow Diagram

For Titanium parts, clean and acid etch per 2.4.

For Invar parts, clean and acid etch per 2.5.

For Aluminum parts, clean and acid etch or anodize per 2.3.

Wrap or enclose parts in approved material.

Bake out (dry) per 2.6 or other GSFC approved method

Apply primer per 2.8 within time (SET) defined in 2.7.

Initial cure primer at room temperature per 2.8.2.

Cure primer at elevated temperature per 2.8.3.

Perform post process inspections per 2.9.

Wrap and store parts in approved material per 2.11.

Perform initial cleaning per 2.2.5.

Grit Blast per 2.2.6.

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2.2 Surface Preparation of Parts- General

2.2.1 General

All surfaces must be thoroughly clean and dry prior to application of the primer. Proper surface preparation is of primary importance in obtaining a satisfactory finish. All abrasive particles and foreign matter shall be removed prior to application of primer. Cleaning shall be accomplished using the solvents and processes specified herein. Parts and surfaces must be primed within the allotted surface exposure time (SET) as defined in 2.7. Reference information on surface preparation is provided in ASTM D 2651.

2.2.2 Racking and Hanging of Parts

Parts shall be placed in a rack, hung, or positioned on a clean, flat surface to insure that 100% of the surfaces where primer is required will contact the cleaning and etching solution. Surfaces where primer is required shall not contact each other or any part of the rack. The rack should only contact areas not being identified as bonding surfaces, i.e. surfaces where primer is not required per the engineering drawing.

2.2.3 Part Handling

Surfaces which require primer (bonding surfaces) should not be touched at any time during the priming process, even by gloved hands. This includes all aspects of the process from etching through the priming steps. If parts must be handled, polyethylene or other non-contaminating gloves are required and contact is permitted only on surfaces that will not be used for bonding.

If contact is made on bonding surfaces, steps performed prior to the contact must be repeated

2.2.4 Cleaning of Parts after Etching

Parts that have holes that have been masked or plugged may have chemical deposits built up inside the holes where the etch solution has leaked into the hole around the masking material.

Such chemical deposits must be rinsed out using de-ionized water and are not permitted on the completed part. Solvents will not remove these deposits. Alcohol may be used to displace the water once the deposits are removed to speed up drying time. If the masking is removed for removal of chemical deposits, replace masking prior to application of primer.

2.2.5 Initial Cleaning of all Metallic Alloys

a) Use alkaline cleaner (such as “Blue Gold” or equivalent), agitated by ultrasonic vibration.

Parts with tapped holes or blind holes shall be pre-cleaned by ultrasonic vibration with degreasing solution.

b) Spray rinse with de-ionized water for 1-2 minutes. Verify cleanliness by water break test and rinse 1-2 minutes again.

c) Electro clean by immersion in alkaline cleaner on direct current for 1-2 min, current density 10 ASF maximum, at 150 +/-10 degrees F.

d) Rinse with de-ionized water for 1-2 minutes. Verify cleanliness by water break test and rinse 1-2 minutes again.

e) Ultrasonically clean with IPA for 15 minutes minimum.

f) Blow dry with GN2 until no IPA is visibly present.

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2.2.6 Grit Blasting for Metallic Parts

2.2.6.1 Dry Grit Blasting

a) Use fresh, 150-grit aluminum oxide media in a clean grit blasting machine.

b) Regulate blast gun pressure to 60 psi +/-10 psi with at least 2x cross coats.

c) Keep surface to be blasted approximately one (1) to three (3) inches from blast gun.

d) Orient blast gun approximately 30⁰ to 45⁰ off normal to part surface.

e) Blast surface until a uniform, matte finish is achieved. Do not dwell more than several seconds at any point on the part surface.

f) Remove the masking tape where applicable from the part. Remove tape adhesive residue with IPA or acetone. If acetone is used, perform final cleaning with IPA.

2.2.6.2 Cleaning Following Post Grit Blasting

a) Remove debris from part surface with clean, dry cloths.

b) Remove debris from part surface by flushing with IPA as required and by using IPA-dampened clean room wipes or cotton tipped applicators.

c) Clean ultrasonically with IPA for 15 minutes minimum until the abrasive and particulate residues are removed. This process may require several cycles of cleaning.

d) Verify that there is no particulate residue being present by wiping with clean room wipe or cotton tipped applicator.

e) Perform water break test with deionized water.

f) Rinse with IPA.

g) Blow dry with GN2 until no IPA is visibly present.

h) Parts shall be wrapped in non-contaminating material for any transporting operations.

Continue to the drying operation.

2.3 Surface Preparation for Priming – Aluminum Alloys

Aluminum parts shall be prepared either by sodium dichromate acid etch as defined in 2.3.1 or by phosphoric acid anodize per 2.3.2. Use of etching solutions and processes other than those defined in this specification is subject to approval by the MEB.

2.3.1 Sodium Dichromate Acid Etch Process

2.3.1.1 Sodium Dichromate Acid Etch Solution

Composition of etching solution shall be as follows:

Ingredient Parts by Weight Oz/Gallon Sodium Dichromate 1 4.0-4.7 Sulfuric Acid (Specific Gravity 1.84)* 10 38.5-40.0 Aluminum Alloy – 2024 Bare 0.2 min Water 30 to make one gallon

* add sulfuric acid to water, stirring slowly

Composition of solution shall be verified at least weekly using the procedures in ASTM D2674.

2.3.1.2 Procedure for Sodium Dichromate Acid Etch

The steps for phosphoric acid anodize preparation of aluminum and aluminum alloy parts shall follow the steps listed below.

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a) Clean per 2.2.5.

b) Plug all tapped holes and holes with tolerances below 0.0005” before etching. Remove any inserts before continuing.

c) Clean parts with acetone by wiping with a clean lint-free cloth (Texwipe 609 or equivalent) or immersing for 5 minutes minimum with acetone.

d) If grit blast is required perform per 2.2.3. GSFC will specify if required.

e) Chemically clean by immersion in alkaline cleaner, agitated by ultrasonic vibration.

f) Spray rinse with de-ionized water for 1-2 minutes. Verify cleanliness by water break test and rinse 1-2 minutes again.

g) Chemically etch by immersion in sodium dichromate acid solution identified in 2.3.1.1 for 12-15 minutes at 145-155 degrees F or by demonstrating removal of 0.0002-0.0004 inches per surface. A witness sample shall be used to verify the removal rate. When the time required to remove the desired amount of material increases 25% relative to that obtained with a freshly prepared solution, the etch solution shall be adjusted or replaced.

h) Spray rinse with de-ionized water.

i) Immerse for 2 minutes in de-ionized water.

j) Cover in an approved non-contaminating material, including polyethylene, Llumalloy, or

Teflon release film.

k) Blow parts with clean dry nitrogen before placing in the oven for drying. Alternate approved drying methods may be used.

l) Bake out per 2.6

2.3.2 Procedure for Phosphoric Acid Anodize (PAA)

The steps for phosphoric acid anodize preparation of aluminum and aluminum alloy parts shall follow the steps listed below.

a) Clean per 2.2.5.

b) Plug all tapped holes and holes with tolerances below 0.0005” before anodize.

c) If grit blast is required perform per 2.2.3. GSFC will specify if required.

d) Clean parts with acetone by wiping with a clean lint-free cloth (Texwipe 609 or equivalent) or immersing for 5 minutes minimum with acetone.

e) Phosphoric acid anodize parts per ASTM D 3933. Note that this process includes cleaning, de-oxidation, rinse and anodize steps.

f) Wrap parts in approved polyester film bagging materials or Teflon film release for bake out.

g) Bake out per 2.6.

2.3.3 Alternate methods for surface preparation of aluminum alloys Alternate methods for surface preparation of aluminum alloys will only be used with approval from the MEB.

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2.4 Surface Preparation for Priming - Titanium and Titanium Alloys

2.4.1 Removal of Re-cast Layer for Titanium Parts Machined by EDM A special process shall be used for removal of any re-cast layer remaining on titanium parts for which Electrical Discharge Machining (EDM) is used for machining of the parts. GSFC will approve the method for removing the EDM re-cast layer and the associated verification method.

2.4.2 Nitric Acid/Ammonium Bi-fluoride Acid Etch Solution for Titanium Alloys Composition of etching solution shall be as follows:

a) Chemically etch by immersion in a room temperature nitric acid/ammonium bi-fluoride solution, consisting of 63% to 70% nitric acid, and the remaining deionized water, with

4.2 to 11.4 oz/gal of ammonium bi-fluoride such that 0.0002” to 0.0004” is removed per surface. A witness sample shall be used to verify the removal rate. When the time required to remove the desired amount of material increases 25% relative to that obtained with a freshly prepared solution, the etch solution shall be adjusted or replaced.

2.4.3 Procedure for Etching of Titanium and Titanium Alloys

The steps for etching of titanium and titanium alloy parts shall follow the steps listed below.

a) Clean per 2.2.5.

b) Plug all tapped holes and holes with tolerances below 0.0005” before etching.

c) Grit blast areas and clean for priming per 2.2.6.

c) Clean parts with acetone by wiping with a clean lint-free cloth (Texwipe 609 or equivalent) or immersing for 5 minutes minimum with acetone.

d) Chemically clean by immersion in alkaline cleaner, agitated by ultrasonic vibration.

e) Spray rinse with de-ionized water for 1-2 minutes. Verify cleanliness by water break test and rinse 1-2 minutes again.

f) Chemically etch by immersion in nitric acid/ammonium bi-fluoride solution identified in

2.4.1 by removing .0002-.0004 inches per surface. A witness sample shall be used to verify the removal rate. When the time required to remove the desired amount of material increases 25% relative to that obtained with a freshly prepared solution, the etch solution shall be adjusted or replaced.

g) Spray rinse with de-ionized water.

h) Immerse for 2 minutes in de-ionized water.

i) Cover in an approved non-contaminating material, including polyethylene, Lumalloy, or

Teflon release film.

j) Blow parts with clean (bottled) dry nitrogen before placing in the oven for drying.

k) Bake out per 2.6.

2.4.4 Alternative Methods of Surface Preparation

Alternative methods of titanium surface preparation, shall be approved by GSFC/MEB before implementing

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2.5 Surface Preparation of Invar Alloys

2.5.1 Etching of Invar

2.5.1.1 Composition of etching solution shall be as follows

Ingredient Parts by Volume Hydrochloric Acid 45.5 ± 5 percent Water 45.5 ± 5 percent Nitric Acid 9 ± 2 percent

* Always add acid to water. The etch solution shall be heated to 131 to 140 ⁰F. This solution shall be constantly agitated

2.5.1.2 Procedure for Etching of Invar

The steps for etching of Invar parts shall follow the steps listed below.

a) Clean per 2.2.2.

b) Plug all tapped holes and holes with tolerances below .0005 before etching.

c) Ultrasonically clean in Blue Gold at 120F for 5 minutes.

d) Chemically clean by immersion in alkaline cleaner 1 to 10 minutes at 160 ⁰F. Apply direct current 1 – 2 minutes at 1 to 6 volts, agitated by ultrasonic vibration.

e) Spray rinse with de-ionized water for 1-2 minutes. Verify cleanliness by water break test and rinse 1-2 minutes again.

f) Chemically etch by immersion in acid solution identified in 2.4.1 by removing 0.0002-

0.0004 inches per surface. A witness sample shall be used to verify the removal rate. This sample shall follow the same process as the bonding material. This would include all heat treats. When the time required to remove the desired amount of material increases 25% relative to that obtained with a freshly prepared solution, the etch solution shall be adjusted or replaced.

g) Spray rinse with de-ionized water for 4 minutes.

h) Ultrasonic clean in 140F de-ionized water.

i) Cover in an approved non-contaminating material, including polyethylene, Lumalloy, or

Teflon release film.

j) Blow parts with clean (bottled) dry nitrogen before placing in the oven for drying.

k) Bake out per 2.6.

2.5.2 Alternative surface preparation for Invar

Grit blast is an alternate method for surface preparation for Invar material. This alternative method will only be used with approval from GSFC.

2.6 Bake-out (Drying) Prior to Priming

2.6.1 Inspection

Parts are required to be placed in an oven for bake-out. Blow parts with clean dry nitrogen before placing in the oven for drying.

Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

Visually examine the parts before drying to ensure that there are no signs of residue on the pieces before drying

2.6.2 Spots

If spots are present, it is acceptable to wipe areas with extracted wipers and de-ionized water. If spots are large or affect the majority of the part, the part shall be re-etched per the applicable etching process.

2.6.3 Bake-out

Place parts in an oven insuring that they do not touch one another or the sides of the oven. Bake the parts at 140-150 degrees F for 60 +15/-0 minutes.

Individually bag parts in non-contaminating material if not primed immediately. Primer must be applied within the applicable time limit in Table 1.

2.7 Surface Exposure Time

Surface exposure time (SET) is the time elapsed between the final step of the etching and surface preparation process and the priming of the parts. SET times for aluminum, Invar, and titanium are identified below.

Table 1. Surface Exposure Time

Material Maximum SET Aluminum Alloys 4 Hours Titanium Alloys 12 Hours

Invar 4 Hours

The start and finish of the SET time shall be recorded on the manufacturing traveler or Certification Log in the appropriate areas for each part

2.8 Primer Application

2.8.1 Preparation of BR127 Primer

The primer shall be stored at or below 0 degrees F and must be allowed to come to room temperature before it is used. Date of shelf life expiration and out time shall be recorded for each container of primer.

Remove BR127 material from freezer. Record time in primer log. When water no longer condenses on the outside of the can of BR127, the container may be opened and used. The container may be placed in a fume hood or in front of a fan to speed up the warming process.

Shake primer thoroughly before pouring into the spray gun reservoir (spray application) or into a container (brush or wiper application). Ensure that the primer is thoroughly mixed prior to application. Primer shall be agitated continually during the application process to ensure proper mixing. Note that solids tend to collect at the bottom of the spray gun. Shaking can be done by hand.

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2.8.2 Primer Application

Ensure that masking is in place to prevent application of primer where marking is required. The relative humidity in the room shall be no greater than 70%. Surfaces shall remain untouched and cleaned per this specification. A fume hood or respirator shall be provided per manufacturer specification.

Primer may be applied by spray gun, brush or wiper. Spray application is preferred. The primer shall be applied to meet the thickness requirements of 2.9.2. The applied film shall be “wet” but not so thick as to result in runs or sags. A thin, uniform coating is optimal. The resulting coat shall be uniform and free of runs.

Initially cure primer at room temperature for 30 to 90 minutes prior to elevated temperature cure.

If additional applications are necessary, the cure time begins after the last application.

Verify proper primer application by comparison to color chart and/or reference inspection standard. The color chart and/or reference standard shall be used during primer application only.

This will give the operator a first metric while the primer is wet. Final inspection will be performed by thickness measurement and acetone wipe.

2.8.3 Primer Elevated Temperature Cure

Place primed part in controlled oven at 250 +10/-10 degrees F for 2 hours minimum. Support of the part shall comply with 2.2.2.

2.9 Post Process Inspections

2.9.1 Visual Appearance

The primer coated surfaces shall exhibit a uniform coating. The coated areas shall be free of runs, sags, and skipped areas.

2.9.2 Primer Thickness

The cured thickness of the primer shall be 0.0002 - 0.0004 inches. Excessive primer thickness will reduce bond strength. This requirement applies to areas where primer coverage is required per engineering drawing.

For areas where primer coverage is optional per engineering drawing, the cured thickness of the primer shall be 0.0002-0.002 inches.

2.9.3 Primer Color

The observed color of the primer shall be consistent with the applicable color chart or reference standard. Visual check of color shall be performed during the process before primer cure and after completion of primer cure. The color charts, if used, are reference checks to ensure proper thickness. Final acceptance will be verified with thickness check.

2.9.4 Acetone Wipe Testing

Proper primer application shall be tested using the acetone wipe method per 3.4.

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2.9.5 Primer Adhesion

A process control witness coupon prepared with the part(s) being processed shall be tested per

3.6 and shall meet the adhesion requirements of ASTM D 3359, rating 4A. There shall be no significant loss of primer coating. For reference, the requirement of ASTM D 3359, rating 4A is as follows:

Acceptable adhesion rating: “Trace peeling or removal along incisions or at their intersection.”

2.9.6 Single Lap Shear Strength

Single Lap shear strength shall meet the requirements of Table 2. A minimum of three single lap shear specimens are required per priming lot. Testing shall be performed per 3.7.

Table 2. Lap Shear Strength Requirements

Primer Substrate Adhesive Tensile Shear Strength psi, Minimum Average

Aluminum Alloy EA 9309 or EA9394 3800 Titanium Alloy EA 9309 or EA9394 3700

Invar EA9309.2NA 3200

2.10 Rework of Damaged Primed Areas

Areas with damaged primer less than 0.25 square inches or 5% of the area requiring primer, whichever is smaller, may be reworked as follows.

Feather the edge of damaged primer with 400 grit aluminum oxide abrasive paper. Care shall be taken to avoid damage to areas outside the area of damaged primer. Solvent clean using acetone followed by isopropyl alcohol until there is no further evidence of contamination. Air dry for 20 minutes minimum. Carefully apply primer using a brush to the damaged area, applying sufficient coats to produce the required dry film thickness. Air dry for 90 minutes minimum at room temperature. Cure at 250 +10/-0 degrees F for 2 hours minimum.

2.11 Storage

After the application and curing of the primer, each part shall be bagged in an approved bagging material and identified with part number and serial number as required per the engineering drawing.

It is recommended, based on information from the primer manufacturer, that properly packaged parts be stored in controlled conditions of 85ºF (29ºC) maximum temperature and 65% maximum humidity for optimum storage life.

The part must be bonded within 6 months of primer application. If the part is not used within the 6 month limit, the time limit may be extended in three month intervals by testing of lap shear specimens prepared with the parts per 2.1.4.2, provided the following requirements are met:

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Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

a) Primed part and primed witness coupons are properly stored in a non-contaminating material and traceability is maintained between the lap shear specimens and the applicable part(s).

b) A minimum of three single lap shear specimens are prepared and tested per 3.7 and meet the requirements of Table 2.

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Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

3 QUALITY ASSURANCE PROVISIONS AND TEST METHODS

3.1 General

The Contractor shall certify compliance with the requirements of this specification. Traceability shall be maintained for materials used in processing parts per this specification. The certificate of compliance shall indicate the type of surface preparation process performed and lot number of primer material. Failure of the parts or test specimens representing the parts to meet the requirements of this specification shall be cause for rejection

3.2 Reference Standard for Visual Inspection

For parts where thickness measurements are difficult, an inspection reference standard may be fabricated by processing a flat sample of the same material and alloy per this specification and testing it per the provisions below. A process control witness coupon per 2.1.4.3 shall be included if the measurement is difficult.

3.3 Appearance

The primed parts shall be visually examined for uniformity of coating, absence of runs, and complete coverage of areas specified on the engineering drawing. Color charts and/or an inspection reference standard shall be used for comparison with the part being inspected.

3.4 Primer Thickness Test Method

The thickness of the primer shall be measured after cure using a Positector 6000 or approved process. For parts where the thickness cannot be measured directly, the primer thickness may be measured using the process control witness coupon defined in 2.1.4.3.

3.5 Acetone Wipe Test Method

Testing of the primer shall be performed using an acetone wipe. Parts shall be wiped using acetone and extracted wipes or Texwipe 609 or equivalent wipes. The wipes shall then be inspected for primer removal. There should be no evidence of primer on the wipe. Some trace amounts of over-spray may give a slight tint on the first wipe. On the second wipe, there shall be no indication of primer removal.

3.6 Adhesion Test Method

Adhesion testing of the primer shall be verified using the process control witness coupon. The testing shall be performed per ASTM D 3359. This method consists of making X- shaped cuts in the primer and applying and peeling pressure sensitive tape, Permacell 99 or equivalent.

3.7 Single Lap Shear Testing

Single lap shear testing shall be performed per ASTM D 1002. Crosshead speed shall be .05 inches per minute. Specimens shall have surfaces prepared, primed and stored identically and concurrently with the flight hardware part(s) as described in 2.1.4.2. The specimens shall be bonded in a suitable fixture using a bond gap of.005-0.010 inches with one of the adhesives specified in Table 2. Shims shall be used to ensure that the test load is applied through the centerline of the specimen.

The specimens shall meet the strength requirements defined in Table 2.

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Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

Lap shear testing is required for initial process approval per 2.1.4.4 and each lot of processed flight hardware parts. Lap shear testing is also required for storage life extension per 2.11, and in the event of processing issues. Periodic lap shear testing is recommended to verify process consistency.

4 NOTES

4.1 Intended use

The process and inspection requirements described herein are intended for use in the application of BR127 primer on spaceflight hardware.

4.2 Typical Drawing Callout

Apply primer WFIRST-IC-SPEC-0062 to surfaces indicated by (flag note and hatch type 1).

Mask surfaces indicated by (flag note and hatch type 2). Primer is permitted but not required (non-bonding surface) on surfaces indicated by (flag note and hatch type 3).

4.3 Preparation for Bonding to Primed Surfaces

Primed surfaces that are not immediately bonded after application of primer shall be solvent wiped with isopropyl alcohol and allowed to dry prior to bonding. Do not under any circumstances use a halogenated solvent, i.e. chloroform, freon, etc. on titanium parts.

4.4 Suggested Source of Supply

Cytec BR127 Primer

Cytec Industries, Inc.

HAVRE DE GRACE, MD

Cytec Engineered Materials Inc.

1300 Revolution Street Havre de Grace, MD 21078 Tel.: (410) 939-1910 Fax: (410) 939-8100

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Use or disclosure of data contained on this page is subject to the restriction(s) on the title page of this document.

Appendix A Abbreviations and Acronyms

Abbreviation/ Acronym

DEFINITION

GN2 Gaseous Nitrogen GSFC Goddard Space Flight Center IPA Isopropyl Alcohol MEB Materials Engineering Branch NASA National Aeronautics and Space Administration SET Surface Exposure Time TBD To Be Determined TBR To Be Revised WFIRST Wide Field Infrared Survey Telescope

2.5.2 Alternative surface preparation for Invar