Plasma Spraying Delamination

[pretzelguy38]

What are the possibilities that cause the surface treated by plasma spraying of aluminum oxide on the 356 Aluminum Alloy? The spraying was only done on the top surface which gets heavy foot traffic. The surface gets cleaned by both alkaline and acid. It also gets salted during winter season. Please advise.

 

[EdStainless]

So this is happening after parts have been in service some time?
I think that you answered your own question, under deposit corrosion.
You could get this verified by some lab work.
What are using as a sealer?
What options do you have for better sealers?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[pretzelguy38]

Thank you. Yes. It has been in service for a few years which is considered very premature.
Original process used Corlar 25P as primer and Imron 333M as sealer.
I personally don't think plasma spraying only on one side is the proper way for the application. And that plasma coating on all sides would have provided a much longer lasting result.

 

[EdStainless]

Is there any flex of these? Is the coating cracking?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[metengr]

Let's see
1. Poor coating quality or problem with the plasma spray.
2. Dirty substrate before coating.
3. Are you sure it is coating spray coating delamination or something else???

 

[pretzelguy38]

@EdStainless
Is there any flex of these? No.
Is the coating cracking? Other than the plasma coating on the top surface the paint and epoxy seem to be intact.

@metengr
I do agree with your #1 and #2. But is there a way to prove it by using the damaged piece as the test subject.
Can you recommend the third party lab that would do this please?

3. Are you sure it is coating spray coating delamination or something else???
I am pretty positive it is the plasma coating that came off because the anti-skid material is gone and what is under looks like raw cast aluminum. Not even with primer or epoxy.

 

[metengr]

Send the damaged piece to a competent met lab for analysis. You asked for possibilities and you may not agree with 1 and 2, but I have seen coating problems that stem from Quality control issues.

I am not sure where you are located. I would send the failed piece to a local metallurgical lab where you can visit and ask questions. You could Fed Ex it anywhere, however, I prefer to be directly involved to view the results.

 

[pretzelguy38]

I do agree with you. Because there is a commercial aspect to the problem, the possibilities must be proven. Can you suggest lab(s) in the New York City Metro area? Thank you.

 

[metengr]

I would say IMR Test Lab, I have actually seen reports from them.

https://www.imrtest.com/locations/ithaca-ny

 

[pretzelguy38]

Thank you!