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Archived for general informational purposes - Originally published April 18, 2003

I recently attended the SAE Aerospace Metals Division Committee B meeting, April 7th in Reno. This is the committee that gets together and argues, pontificates, cajoles, rambles, deliberates, and eventually writes the Aerospace Materials Specification (AMS) documents that many companies use to control materials and processes. I believe that a few of the results will be of interest to finishing dot com readers.

Realize that after Committee B finishes it's technical deliberations, then the documents are voted on by the Aerospace Council, a group composed of representatives of aerospace companies and Government agencies. ASC approval is usual, but not a foregone conclusion. After ASC approval the new document, or new revision, will be published. This process usually takes a while. Spec writing is not for the impatient.

So, IF approved by Aerospace Council, the following changes to AMS documents will eventually be published:

• Among other changes, AMS 2430 on shot peening was changed to allow only automatic or machine controlled peening. Provisions for shot peening manually, using a hand held nozzle, were removed.
• AMSC5541 was canceled, and the cancellation notice states that it is superseded by Mil-C-5541.
• Likewise, AMSA8625 was canceled and superseded by Mil-A-8625.
• AMS-QQP35 was canceled and superseded by AMS 2700. At the same time,
• AMS 2700 is being revised to bring the Type VI nitric acid content into line with what QQ-P-35C had, which was 25 to 45%. AMS 2700 allows citric acid passivation IF it is called out by the customer: nitric acid remains the default processing. AMS 2700 also brings back the rest of the old withdrawn recipes; so Milt, you've got your Type IV back! One thing that AMS 2700 specifically did NOT add from the old QQ-P-35 was the chart of recommended solutions for each of the stainless steels. One of those can be found in ASTM A-967, or just hang on to your olde copy of QQ-P-35.
• The draft specification for a low electrical resistance chemical conversion coating for aluminum (somewhat comparable to Mil-C-5541 type 3) remains active, and will be continued at the Fall meeting in Montreal.

After the technical deliberations, Lee Kremer gave a presentation to the Committee on the wonders of citric acid passivation, which made some very interesting claims backed up by ESCA (XPS) and Auger Electron Spectroscopy, two high powered surface chemistry techniques. Apparently the chromium to iron ratio, as well as the chromium oxide to iron oxide ratio, are greater with citric acid than with nitric acid passivation. I was surprised at the extent of Mr. Kremer's laboratory data, which supported the results of the corrosion testing he's done. As he advertises on finishing dot com, it won't be hard to find out more about the process he sells. Contact him for more information on the process or on the data he presented. -- L.G.