Powder-coat tail spring

Greetings, I am getting ready to mount the tail spring and tailwheel assembly. This unit lives in a rather harsh environment and I would like to put a power-coat finish on it. I am wondering if the heat used in the process would have any affect on the spring temper? Thanks, Don Owens

tail wheel

What a few have been doing around here is to chrome the tail wheel. Very durable and very sexy.

I used to oversee a powdercoat process on an assembly line. I would guess the cure temperatures for metal that thin (relatively speaking) would be in the neighborhood of 300 F for a pretty short time (15-30 mins). Maybe even less.

Don't have any material books handy but I'm guessing that would not affect the mechanical properties of the steel.

For 250 # A/C compressors, we baked at over 400 F for 75 minutes. These were very dense steel parts.

What I wonder about is the durability of the coating on a part that flexes in tension like a spring...possibile cracks? Coating thickness would be a consideration here.

Find a good powdercoat shop for advice & ask about their cure schedule.

Good luck.

Chrome plating high carbon steels can cause hydrogen imbrittlement. I was a machinist/tool maker for several years and have seen chrome plated induction hardened rods form cracks during a simple annealing process. I would not chrome plate any steel part on an airplane that would come under any stress, such as a tailwheel spring, or landing gear parts. A nice looking Cessna 140 had a chrome plated landing gear leg break off during a normal landing not too long ago. Just a piece of information to consider.

Powdercoating

I run a powdercoat booth and batch oven in my business. www.cpltoolbox.com. Most of the paint I have applied over the years has cure schedules at about 350-400 degrees F for 10-15 minutes. The important thing is the 350-400 degrees is metal temp. We use a infrared thermometer and start the recommended 10-15 minutes timing or whatever the paint calls for on the spec sheet once the metal reaches temperature. I do not believe that it would ever alter the properties of the metal...not near hot enough. However powder coat will crack if applied to thick. It would work fine if a polyester or polyurethane powdercoat was used and applied no thicker than 3 mil. This info should not be taken for gospel this is just what we have found in 10 years of powdercoating experience. Anytime you have something powdercoated make sure the applicator is following the guidelines on the spec sheet for that powdercoat. If he does not have a spec sheet have him get it and follow it. Most powdercoat has pretty good overbake tolerances but I have found poor underbake tolerances. Whenever I get anything unique in my oven I always use the infrared thermometer to check metal temps. One other question I get asked alot is if you can powdercoat over other paint, powdercoat, chrome, etc. Yes you can for the most part, however I do not like to as I don't believe the paint sticks as well. Alot of times it will not smooth out as pretty if it is over some other paint. Show me powdercoated items and 9 times out of 10 I could tell you whether or not the powdercoat was applied over a existing paint.
Powdercoat websites:
www.tigerdrylac.com
www.spraylat.com
www.govesan.com

hydrogen imbrittlement

hngrflyr said:

Chrome plating high carbon steels can cause hydrogen imbrittlement. I was a machinist/tool maker for several years and have seen chrome plated induction hardened rods form cracks during a simple annealing process. I would not chrome plate any steel part on an airplane that would come under any stress, such as a tailwheel spring, or landing gear parts. A nice looking Cessna 140 had a chrome plated landing gear leg break off during a normal landing not too long ago. Just a piece of information to consider.

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Very true hngrflyr...I am speaking from experience now, the gentleman I bought my partially completed 6A from had chromed the rudder petal hangars without any vent hole. (This was before Van's released the update to weld the reinforcements on) I had heard of hydrogen imbrittlement and was curious, so I took the hangars to the vise and gave them a good checkover. Results....several small cracks right around the welds. This airplane had not been flown and the pedals had only been pushed on for dreaming sake prior to this. I bought new rudder pedal hangars without hesitation.

Good advice hngrflyr!

Finish of steel tail wheel rod

I vote for a good, prep, epoxy primer and paint the same color as the airplane, if only for looks, as the mono-chromatic looks takes attention away from the tail wheel assembly vs making it flashy and a standout.

From a corrosion stand point the painted finish should be as durable as any and readily applied or reapplied if needed. I don't know about powder coat, except what I see from vans parts. It seems to be thick and prone to chip? I know of hydrogen embitterment as a former aerospace engineer. You need the right environment, exposed end grain for this to happen. If plating is done properly the risk is minimized, but with the examples mentioned sounds like chrome is not a good idea. Cheers G