**Process Specification for the Sealing of Joints and Faying Surfaces**

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| **Engineering Directorate**                                           |
|                                                                       |
| **Structural Engineering Division**                                   |
|                                                                       |
| **August 2006**                                                       |
|                                                                       |
| ![](media/image1.png)                                                 |
|                                                                       |
| National Aeronautics and                                              |
|                                                                       |
| Space Administration                                                  |
|                                                                       |
| **Lyndon B. Johnson Space Center**                                    |
|                                                                       |
| Houston, Texas                                                        |
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**Process Specification for the Sealing of Joints and Faying Surfaces**

+--------------+------------------------------------+---+--------------+
| **Prepared   | ***Signature on File***            |   | ***8/3/06*** |
| by:**        |                                    |   |              |
+--------------+------------------------------------+---+--------------+
|              | Jay E. Bennett                     |   | Date         |
|              |                                    |   |              |
|              | Materials and Processes Branch     |   |              |
|              |                                    |   |              |
|              | ES4                                |   |              |
+--------------+------------------------------------+---+--------------+

+--------------+------------------------------------+---+--------------+
| **Approved   | ***Signature on File***            |   | ***8/3/06*** |
| by:**        |                                    |   |              |
+--------------+------------------------------------+---+--------------+
|              | Bradley S. Files, Chief            |   | Date         |
|              |                                    |   |              |
|              | Materials and Processes Branch     |   |              |
|              |                                    |   |              |
|              | ES4                                |   |              |
+--------------+------------------------------------+---+--------------+

  ----------- --------------------------------------------- ---------------
  REVISIONS                                                 

  VERSION     CHANGES                                       DATE

  \--         Original version                              2/19/98

  A           Addition of Aeroglaze 9743/9700 primer.       4/19/99
              Addition of addresses and CAGE codes for      
              sealant vendors.                              

  B           Modified paragraph 3.1, Clarified sealing of  7/14/00
              helical wire inserts in sections 6.5 and 8.0, 
              updated part number for Super Koropon in      
              section 3.0                                   

  C           Changed Division name. Revised section 3.1    10/2004
              (Work Instructions) and moved to section 6.1, 
              renumbered section 6, and revised section 9.0 
              (Training).                                   

  D           Deleted Aeroglaze 9741 as an approved primer. 8/2006
              Changed JPG-8500.4 to JPR-8500.4 Added part   
              numbers to material references. Updated       
              manufacturer of Koropon to PRC Desoto. Added  
              pot life & mixing ratio & thinning            
              information in section 6.8. Added detail on   
              rivet application in section 6.5.             

                                                            

                                                            
  ----------- --------------------------------------------- ---------------

**1.0 [SCOPE]{.underline}**

This process specification establishes requirements for the sealing of
joints and faying surfaces for the purposes of moisture exclusion,
corrosion protection or the containment of gas pressure.

**2.0 [APPLICABILITY]{.underline}**

This process specification shall be applicable whenever the sealing of
joints and/or faying surfaces is invoked per Section 3.0, "Usage".

**3.0 [USAGE]{.underline}**

The use of a sealant is standard practice between the faying surfaces of
dissimilar metals. It is also standard for aluminum joined to aluminum
when the surfaces are not already coated with a corrosion resistant
organic primer. It is also standard for primed aluminum surfaces when
the assembly will be used in a wet or humid service environment.

Examples of common sealant usage include:

Faying surface sealing of joints between conversion-coated aluminum
parts.

Faying surface sealing of joints between anodized aluminum parts.

Sealing a stainless steel hinge to an anodized aluminum part.

Sealing stainless steel bolts in an anodized aluminum part.

Sealing aluminum or steel rivets in primed aluminum sheet.

Sealing stainless steel inserts in aluminum parts.

Sealing stainless steel bearings in aluminum parts.

This process specification shall be called out on the engineering
drawing by using an appropriate drawing note. The specific process and
sealant shall be included in the drawing note. For example:

**SEAL FAYING SURFACES WITH AEROGLAZE 9743/9700 PER NASA/JSC PRC-4004.**

**SEAL FAYING SURFACE WITH PR1440C PER NASA/JSC PRC-4004.**

**SEAL FASTENERS WITH AEROGLAZE 9743/9700 PER NASA/JSC PRC-4004.**

**SEAL INSERTS WITH SUPER KOROPON PRIMER BASE PER NASA/JSC PRC-4004.**

**SEAL RIVETS WITH AEROGLAZE 9743/9700 PER NASA/JSC PRC-4004.**

**SEAL BUSHING WITH AEROGLAZE 9743/9700 PER NASA/JSC PRC-4004.**

Faying surface sealing is normally performed simultaneously with the
sealing of the fasteners that clamp the joint together. When used in
conjunction with a fastener or mechanical part installation
specification, this sealing note shall immediately follow the
appropriate installation note. For example:

**INSTALL THINWALL SCREW THREAD INSERTS PER NASA/JSC PRC-9004. SEAL
INSERTS WITH AEROGLAZE 9743/9700 PER NASA/JSC PRC-4004.**

As shown in the examples above, the specific sealant selected is
identified by including a short description in the drawing note. The
standard sealants and configurations used at JSC are as follows:

Faying Surfaces: [Aeroglaze 9743/9700]{.underline}

Super Koropon Primer Base

Super Koropon Primer

PR1440C

Threaded Fasteners: [Aeroglaze 9743/9700]{.underline}

Super Koropon Primer Base

Super Koropon Primer

PR1440C

Threaded Inserts: [Aeroglaze 9743/9700]{.underline}

Super Koropon Primer Base

Super Koropon Primer

Rivets: [Aeroglaze 9743/9700]{.underline}

Super Koropon Primer Base

Super Koropon Primer

PR1440C

Bushings, Bearings: [Aeroglaze 9743/9700]{.underline}

Super Koropon Primer Base

Super Koropon Primer

The preferred sealant is [underlined]{.underline}.

When Super Koropon Primer is used without the curing solution, it is
called "Super Koropon Primer Base." Used by itself, the primer base
dries but does not cure, which allows fasteners and faying surfaces to
be disassembled.

Aeroglaze 9743/9700 product is not fully catalyzed which will promote
disassembly of sealed joints.

Nonstandard sealant materials (those not listed above) may be used, but
should be reviewed in advance with Materials and Processes Branch (ES4)
personnel.

A complete description of the sealing material shall be called out in
the parts list on the engineering drawing, as follows:

+-------------------+--------------------+----------+-----------------+
| Part number       | Description        | Material | Specification   |
+-------------------+--------------------+----------+-----------------+
|                   |                    |          |                 |
+-------------------+--------------------+----------+-----------------+
|                   |                    |          |                 |
+-------------------+--------------------+----------+-----------------+
| Aeroglaze         | Epoxy Primer       |          |                 |
| 9743/9700         |                    |          |                 |
+-------------------+--------------------+----------+-----------------+
|                   |                    |          |                 |
+-------------------+--------------------+----------+-----------------+
| Super Koropon     | Epoxy Primer Base  |          |                 |
| 515-700           |                    |          |                 |
+-------------------+--------------------+----------+-----------------+
|                   |                    |          |                 |
+-------------------+--------------------+----------+-----------------+
| Super Koropon     | Epoxy Primer       |          |                 |
| 515-700/910-704   |                    |          |                 |
+-------------------+--------------------+----------+-----------------+
|                   |                    |          |                 |
+-------------------+--------------------+----------+-----------------+
| PR1440 C-20       | Polysulfide        |          | MIL-S-8802      |
|                   | Sealant            |          |                 |
|                   |                    |          |                 |
|                   | Base and           |          |                 |
|                   | Accelerator        |          |                 |
+-------------------+--------------------+----------+-----------------+
| PR-182            | Adhesion Promoter  |          |                 |
+-------------------+--------------------+----------+-----------------+

Aeroglaze 9743/9700 is currently manufactured by the Lord Corporation,
which has changed the product labeling of their 9700 series products.
The Part B (hardener) for Aeroglaze 9743 is now designated Aeroglaze
9700 rather than Aeroglaze 9741. Super Koropon Primer (both primer base
515-700 and curing solution 910-704), PR1440C, and PR-182 are
manufactured by PRC Desoto.

Lord Corporation

Cary, NC 27512

CAGE Code 9J509

PRC Desoto Aerospace Coatings

Glendale, CA 91209

CAGE Code 83574

Surface preparations that are appropriate for sealant application are:
cured epoxy primer, anodized aluminum, chromate conversion coated
aluminum, and bare metals. When a new sealing technique is developed for
a specific surface preparation, it shall be verified to produce
acceptable results and then documented in the appropriate work
instruction.

**4.0 [REFERENCES]{.underline}**

All documents listed are assumed to be the current revision unless a
specific revision is listed.

SOP-007.1 *Preparation and Revision of Process Specifications*

JPR 8500.4 *Engineering Drawing System Manual*

1.  **[MATERIALS REQUIREMENTS]{.underline}**

No special materials are needed for this process. Sealant material shall
be specified on the engineering drawing.

**6.0 [PROCESS REQUIREMENTS]{.underline}**

## 6.1 WORK INSTRUCTIONS

All work shall be performed to written procedures. The work instructions
shall contain sufficient detail to ensure that the manufacturing process
produces consistent, repeatable products that comply with this
specification.

For work performed at JSC facilities, these work procedures consist of
Detailed Process Instructions (DPI's).

For contracted work, the contractor shall be responsible for preparing
and maintaining, and certifying written work procedures that meet the
requirements of this specification.

**6.2 GENERAL REQUIREMENTS**

The surfaces to be sealed must be cleaned with an appropriate solvent
prior to sealant application. In addition, the sealant must be used
while it is still wet and within its potlife requirement.

The joint shall be assembled and the excess sealant shall be removed to
achieve a smooth fillet at the exposed joint.

**6.3 FAYING SURFACE SEALING**

For faying surface sealing, the sealant shall be applied to one or both
sides of the metallic joint, as referenced on the drawing, before
assembly.

**6.4 FASTENER SEALING**

For threaded fasteners, sealant shall be applied to the bottom surface
of the head, the fastener shank, the underside of the washer(s), as well
as the interior surfaces of the hole and countersink. Threads shall be
kept free of sealant, so in some cases it may not be possible to coat
the hole completely.

**6.5 RIVET SEALING**

For rivet sealing, sealant shall be applied to each rivet shank and
under the head before it is inserted into its corresponding hole.

**6.6 INSERT SEALING**

Sealant shall be applied to both the hole and any existing countersink
before a key-locked insert is inserted.

Sealant shall be applied to the external surfaces of thinwall inserts
before they are inserted.

Sealant shall be applied in a thin coat only to the fastener hole before
helical wire inserts are installed. Extra care shall be used to preclude
sealant from transferring to the internal threads of the insert.

**6.7 BEARING AND BUSHING SEALING**

Sealant shall be applied to both the bore and the outside diameter of
the bearing or bushing.

**6.8 SEALANT-SPECIFIC REQUIREMENTS**

The ratio of Aeroglaze 9743 mixed with Aeroglaze 9700 hardener shall be
modified to 20:1 by weight (with a tolerance of ± 2% by weight on the
9743). The lower percentage of hardener produces a weaker cure to
improve removeability of fasteners and faying surfaces sealed with the
primer.

The ratio of Super Koropon Primer Base to Super Koropon Primer Catalyst
shall be 1:1 by volume (with a tolerance of ± 5% by volume).

Mixed Sealant pot life for Super Koropon Primer shall be limited to (8)
eight hours after mixing. Mixed Sealant pot life for Aeroglaze shall be
limited to (8) eight hours after mixing.

Super Koropon Primer Base (used without the curing solution) pot life is
only limited by the consistency of product. When it becomes too thick to
apply, it may be may be thinned one time with MEK at a ratio of 2 -- 5%
MEK per primer by volume for ease of application as detailed in the work
instructions. If thinned once and becomes too thick to apply, it must be
discarded.

PR1440-C20 is used to provide an airtight seal for cabin pressure.
PR-182 adhesion promoter shall always be used with the PR1440-C20. The
surface shall be prepared so that the adhesion promoter will wet the
surface. The adhesion promoter shall dry for 15 minutes before the
PR1440 is applied. The PR1440-C20 shall be applied within 24 hours after
the PR182 is applied.

**7.0 [PROCESS QUALIFICATION]{.underline}**

The sealing process shall be qualified and accepted prior to assembly of
production parts. This qualification shall provide documented evidence
that the installation procedures are capable of meeting the requirements
of this process specification and the engineering drawing. Any change to
the procedure shall require requalification.

**8.0 [PROCESS VERIFICATION]{.underline}**

Verification of proper sealant application shall consist of inspection
to ensure that the dried sealant forms a continuous fillet on the
surface between the parts being joined.

When using PR1440C, verification that the adhesion promoter wets the
base surface in a continuous manner and does not bead up is also
required. In-process verification coupons are required for PR1440C
application.

When a sealant is used with helical wire inserts, a lot verification
using a swab shall be performed to determine if sealant has transferred
to the internal threads of the insert. If sealant is found, all inserts
installed in the lot shall be checked and the sealant shall be removed
if necessary before the sealant has completely cured.

**9.0 [TRAINING AND CERTIFICATION OF PERSONNEL]{.underline}**

This process shall be performed by personnel qualified through training
or experience and certified by their supervision to conduct the process.

**10.0 [DEFINITIONS]{.underline}**

Epoxy primer Paint containing epoxy resin that is applied to joints
and/or faying surfaces for corrosion resistance; one example is Super
Koropon primer .

Faying surfaces Mating surfaces, including the mating surfaces of a
fastener joint.

Primer base Primer that is used without catalyst or curing agent.