Home Forums General Discussion Specifications de-contamination of aluminum after peening

Re: AMS-2432 Rev B
Section 3.6.3.1.2

Does anyone use the following procedure to de-contaminate aluminum after shot peening? The amount of in-solution time is not mentioned in the spec. What is your standard practice? This topic will be discussed at the next meeting of AMEC in Asilomar on February 2,3 and 4 2005.

Aluminum alloy parts shall be decontaminated in a 50% ± 5 % by volume nitric acid solution at ambient temperature or 20% ± 2 by volume nitric acid solution at 140 F ± 5 (60 "C ± 3), rinsed with hot (140 F (60 C) agitated water, and dried. Alternatively, glass beads may be used for decontamination when approved by the cognizant engineering organization.

This is the method we use for cleaning for aluminum for an airframe mfg.

Per XXX-XXXX Method X, solution 13A, immerse parts in nitric acid (Technical 42 degree Be) at room temperature for 10 to 40 minutes. Time should be the minimum required to remove traces of shot peen residue.

Another method used for a Helicopter Mfg is:

Nitric acid clean (20-50% nitric / water) at 140±10 degrees. F. for 20-40 minutes, then water rinse. As an alternative, glass bead peen at .002-.006N. 20-30 PSI with #13 glass.

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MIL-P-81985 "Peening of Metals" states in section 3.5.2.1 "Aluminum parts. Unassembled aluminum and aluminum alloy parts without inserts may be cleaned by immersion in a nitric acid solution for 20 to 40 minutes at 120° to 140°F (49° to 60°C). The solution shall consist of the following:

nitric acid( (Sp. gr. 1.42) 200 to 500ml.
Water to make 1.1

Nitric acid base deoxidizer solutions used prior to the application of anodic and chemical conversion coatings may be used provided they meet the acid strength requirements (see 6.14)

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