Powder Coat on 4130

On Apr 8, 3:26 pm, " wrote:
On Apr 1, 4:16 pm, John T wrote:



Responding to an "old" thread here, but powdercoat cures at about 400
deg. F.
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Whoa. 'Powder-coating' is a generic term that applies to everything
from ceramic frits to vinyl. The temperature/atmosphere needed to
cause the powder to melt and flow together can be anything from 150
degrees to over a thousand degrees.

Key point here is that all 'powder coating' is not the same. Some
shops use but a single type of coating, say a urethane. Others may
offer a variety of coatings, from low-temp vinyls to chemically inert
epoxies.

You CAN do it at home -- it is easier than applying ceramic thermal
barrier coatings. But you have to know what you're doing. Most of
the information (and mis-information) commonly available has to do
with vehicular applications done mostly for the sake of appearance,
most of which have no place anywhere on an airplane. But it's the
cat's pajamas for things like a battery box, cabin fixtures and the
like.

-R.S.Hoover

Excellent points. If someone tries to use a 1000 deg temp process to
powder coat a heat treated steel part, then the heat treatment will
almost certainly be lost, as even some of the highest strength, high
temperature alloys start to lose temper at as low as 800 F. Also, the
chemical reaction caused by exposure to high tempearture and the
presence of the materials that are being used to "powder coat" the
steel could cause God knows what to the surface of the steel. Hydrogen
or nitrogen embrittlement comes to mind. For lightweight structure
that your life depends on, you need to KNOW.
Many builders have their 4130 steel parts annealed after welding
by heating the structure to a cherry red temp and slowly reducing the
heat, in order to relieve any stress concentrations created during
welding. People that have powder coated normalized 4130 probably are
OK, even at 1000 F, but you never know for sure until a chemical study
of the effect has been done.

Bud