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Troubled Phosphate Solution and Aerocote 4

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Q. Hello,
My name is Andrew. I work at a machine shop where assault rifles are manufactured in Salt Lake City, Utah. My question was regarding the phosphate solution we use here to coat our steel rifle parts (such as the barrel, trigger parts, and other internals) and turn them black. The solution we use is made by a company called Nalco and it is called Aerocote 4. All that we put into the dipping tank is water and the Aerocote 4. The only thing we do before dunking is sandblast the parts with 100 grit aluminium oxide. Since I've worked here, no one has ever really given me proper training on maintaining the solution and I've mostly had to figure it out for myself. Recently I went to phosphate some rifle barrels and the finish didn't turn out so great. By that I mean the barrels didn't have a solid black finish and they looked really grainy. The only thing I can think of doing is cleaning the tank and adding more solution, but I don't want to just keep wasting it. If anyone has any information or advice they can share with me, it would be much appreciated. Thank you.

Andrew Ellsworth
shop employee - Salt Lake City, Utah, United States of America
2007

A. All major manufacturers like Nalco generate technical data sheets (instructions on operating conditions) as well as MSDS sheets (material safety data sheets) for each of their products, Andrew. The first step is just to ask them for a tech data sheet and MSDS for Aerocote 4. I don't know your position with your company, and whether you need to get approval from a supervisor, but you can ask a rep to come in to talk to you about the product.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

? Hi Andrew,

Can you describe the parameters of your process in greater detail, like contact time, temperature and concentration? This will help in troubleshooting your problem. Aerocote 4 is a fairly easy product to run, so it should be simple to get you back on track.

George Gorecki
- Naperville, Illinois
2007

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