Dear Dr. Peener,
I am a service engineer and we are a repair and overhaul facility for gas turbine engines and propeller assemblies.

We currently use Electronics Inc. "Y" Test Strips, P/N 970060.3, when qualifying some of our shot peen applications throughout our company and are very pleased with your product.

I am currently working on an R&D project and I was hoping you could answer some technical questions with regards to the use of shot peen media. Our overhaul data directs us to use either 550 cast steel shot or LD62 conditioned cut wire steel shot for peening applications. Note that I have not been able to find any reference anywhere referring to LD62 shot and I do not know if such a product exists. The material that we are peening is 7076-T61 Aluminum alloy.

Once the shot peening is complete, an iron decontamination process must be completed and an iron decontamination check follows to ensure there are no traces of iron remaining.

What I am looking at is to see if stainless steel shot can be used in place of the shot types listed above. In particular using SCW 62 Conditioned Stainless Steel (Type 302) Cut Wire Shot.

1) Would you know if this is a recommended product for shot peening aluminum alloys?

2) Is it known if this stainless media can contaminate an aluminum alloy surface much like cast iron / steel shot will from the shot peen process?

3) If there is a chance for surface contamination due to using stainless steel shot on aluminum alloys is there any known product that will remove the stainless steel contamination - much like using a Deoxidine / MetalPrep solution or a Sodium Hydroxide solution to remove iron contamination from aluminum alloys after shot peening.

4) Are there any process that can be performed to check for stainless steel contamination on aluminum alloys - much like current iron decontamination checks.

The reason I ask these questions is that if one looks at the galvanic difference between aluminum and type 302 stainless steel one will see that this difference is quite large. When this difference is large the galvanic corrosion rate is highly elevated. Thus we are unsure if the stainless steel contaminants (if any) on the aluminum surface could be detrimental.

Your help in this matter would be greatly appreciated.

Jack Champaigne (Dr. Peener)
Editor The Shot Peener