Process Specification for the Chemical Conversion Coating of Aluminum
Alloys

+-----------------------------------------------------------------------+
| Engineering Directorate                                               |
|                                                                       |
| Structural Engineering Division                                       |
|                                                                       |
| December 2007                                                         |
|                                                                       |
| ![](media/image1.wmf){width="0.9444444444444444in"                    |
| height="0.8055555555555556in"}                                        |
|                                                                       |
| National Aeronautics and                                              |
|                                                                       |
| Space Administration                                                  |
|                                                                       |
| ###### Lyndon B. Johnson Space Center                                 |
|                                                                       |
| Houston, Texas                                                        |
+-----------------------------------------------------------------------+

**Process Specification for the Chemical Conversion Coating of Aluminum
Alloys**

December 2007

  ------------------ -------------------------- ----- --------------------
  **Prepared by:**                                    

                     John Figert, Materials &         Date
                     Processes Branch/ES4             
  ------------------ -------------------------- ----- --------------------

  ------------------ -------------------------- ----- --------------------
  **Approved by:**                                    

                     Bradley S. Files, Chief          Date
                     Materials and Processes          
                     Branch/ES4                       
  ------------------ -------------------------- ----- --------------------

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

  VERSION     CHANGES                                       DATE

  \--         Original version                              5/15/96

  A           Reviewed and update for accuracy; Author      7/21/99
              changed                                       

  B           Limited the brush application for conversion  8/25/05
              coating in section 9.0                        

  C           Reviewed and updated for accuracy. Deleted an 
              obsolete "Prepared by:" signature block and   
              updated the MIL specification number.         
  ----------- --------------------------------------------- ---------------

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

This process specification establishes technical requirements for the
application of chemical conversion coatings on aluminum and aluminum
alloys.

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

This process specification covers the requirements for two classes of
chemical conversion coatings formed by the reaction of chemical
conversion materials and the surfaces of aluminum and aluminum alloys.
Conversion coatings covered by this specification are intended to
provide increased corrosion resistance and/or a surface having better
paint adhesion than uncoated aluminum. They are not intended to be used
for decorative applications.

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

This process specification shall be called out on the engineering
drawing by using a drawing note that identifies the process
specification and class and the conversion coating to be used. For
example:

The two classes of chemical conversion coating are:

Class 1A For maximum protection against corrosion, for surfaces to be
painted or left unpainted

Class 3 For protection against corrosion where lower electrical
resistance is required

## 3.1 [WORK INSTRUCTIONS]{.underline}

Work instructions shall be generated for implementing this process
specification. The work instructions shall contain sufficient detail to
ensure that the manufacturing process produces consistent, repeatable
products that comply with this specification.

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

None.

**5.0 [SAFETY PRECAUTIONS AND WARNING NOTES]{.underline}**

As specified in MIL-DTL-5541F.

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

The following references were used to develop this process
specification:

##### SOP-001.2 Preparation and Revision of Process Specifications

JSC 8500C Engineering Drawing System Requirements

The following documents are called out as an extension of the
requirements given in this specification:

MIL-DTL-5541F Detail Specification, Chemical Conversion Coatings on
Aluminum and Aluminum Alloys

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

As specified in MIL-DTL-5541F.

**8.0 [PERSONNEL TRAINING AND CERTIFICATION]{.underline}**

All chemical conversion coating of aluminum alloys shall be conducted by
trained personnel.

**9.0 [PROCEDURE]{.underline}**

All chemical conversion coating of aluminum alloys shall be conducted in
accordance with MIL-DTL-5541F, except that immersion coatings shall be
used for new part manufacture exclusively. Brushed-on conversion
coatings are only acceptable for applications specifically stated on the
drawing and for minor touch-up repairs documented and resolved on a
discrepancy report (DR).