Powder coating parts

[johnpstoll]

I am considering powder coating some of the aircraft parts. I?m told that the part will be baked at 400 degrees during the process. My question is, is it advisable to powder coat aircraft parts or will the process weaken the metal?

Thanks,

John

[az_gila]

Originally Posted by johnpstoll

I am considering powder coating some of the aircraft parts. I?m told that the part will be baked at 400 degrees during the process. My question is, is it advisable to powder coat aircraft parts or will the process weaken the metal?

Thanks,

John

....no problem. The aluminum parts might change their temper...

[RScott]

Long story, but it might help:

It was a cold winter day when I lit up my 35,000 BTU free standing propane heater, then set my HS on the work table. After just a few seconds, I realized that part of the HS extended directly over the heater. Of course I quickly removed the HS.

Hmmm, now what? AC 43.13 says don't heat aluminum over 212 deg. F. Same temp as boiling water. I wonder how they arrived at that number?

Searched the internet for info on whether I did any damage; no luck.

But at the Air Guard, where I had worked before retirement, we had an eddy current tester that can be used for sorting alloys, although we never used it for that, so we had no experience with that function--we just used it for checking for cracks. Called the shop chief; he said "bring it on down, we'll figure it out".

I took a piece of scrap of the same thickness, extended it over the heater for about twice as long as I estimated the HS was there. I set another piece there and checked the temp and it was somewhere around 400 deg., but my measurement ability was pretty crude. It was a small piece and the skin on the HS may have dispersed the heat more than my test piece.

At the AG, by dumb luck there was a gal from the AF Reserve who happened to be there & they had just had occasion to use the eddy current machine for checking heat treatment, so she knew how to run the test.

There is a range of acceptable numbers for T-3, but I don't remember the range or the scale, so let's just say it ran from 1-10. Unheated portions of the HS ran, let's say, 5 and the heated area may have been 3 or 4, still in the acceptable range for T-3. My test sample was closer to the limit.

That was after only a few seconds exposure to the heat.

So my experience suggests 400 deg. will change the temper, so I wouldn't powder coat any structural parts.

[noelf]

...of steel parts using the Eastman stuff. The aluminum parts that I powder coated were non structural...only cosmetic items. Depending on the powder type, the baking temperatures can range from 375 to about 500 deg F, and the bake time is in the 25 35 minute range. I would not powder coat any structural aluminum items due to the heat treatment process that will change the temper of the materials.

[powdercoater]

John:
We are a custom powder coating facility in Los Angeles that has done many powder coating jobs on civilian as well as military aircraft parts. We are currently being used for data that will be used to change Navy specifications (just the first branch, the others will follow) from high VOC liquid paints to powder coatings.

The powder coating service that is selected is more important than the general question of how will a part withstand the process. The service provider should be able to understand the type of part that is being coated and what its uses are going to be on any given aircraft. There are differing preparation techniques and also differing powder coatings that will be used for parts depending on their service. Sometimes the combination of a plating process and powder coating is in order.

But to give a general answer on the subject of whether parts will be negatively impacted by the heat of the powder coating process is rarely. But we have seen non-ferrous parts destroyed by people that do not understand basic metallurgy and they will operate the oven at higher than standard temperatures and then make the dwell times too long. This will cause aluminum to loose some of its tempering characteristics. We are not engineers here and do not pretend to be, but we have years of experience in seeing these items and having many discussions with engineers and education through various powder coating classes.

With proper technical data from the manufacturer and the proper preparation, powder coating materials and oven control with testing procedures, the ability to coat aircraft parts with powder coatings is very safe. But not following proper procedures will have terrible results.

In fact we have done landing gear in the past, and this is the area that the Navy is looking into using powder coating on titanium parts. When doing aluminum parts we will use lower temperatures and if the parts are structural the powder coating will be specific to the parts with engineering oversight.

Again, we are not claiming to be an engineering firm and this is general information on our past experiences. But the reality is, choose your powder coating service provider carefully. EZ bake oven processing with a $199 Harbor Freight powder coating system is not a good idea.