Phosphate or Chromate?

Timbeck2

Timbeck2

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Timbeck2
I know google is your friend but my "friends" here have more knowledge. So what is the difference in the two other than price? Which one is used more in protecting GA aircraft?
 
Okay I looked it up on google anyway:

Phosphate coating is a widely used alternative treatment to increase corrosion resistance and improve adhesion of the paint coatings on zinc, iron and its alloys (2). Phosphate coatings do not work as well as chromate coatings do; anyhow, they are less harmful to the environment.

When in doubt I usually go for the most expensive which is chromate, but I do fear for the children.
 
Timbeck2 said:
So what is the difference in the two other than price?
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Any product containing chromate or dichromate is severely restricted or prohibited to manufacture now. Prior to the new regs years ago on chromate, the story goes the mfg'rs of zinc chromate paint made 10M gallons to last awhile. Story is they're down to the last 2M gallons and the price went up.

Timbeck2 said:
Which one is used more in protecting GA aircraft?
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In my experience for a single part paint, chromate based. However, new two-part epoxy primers are now better.
 
IMO, two part epoxy has always been better but grabbing a can of zinc chromate for a quick, small job is what typically happens (if you can find it).
 
Bell206 said:
In my experience for a single part paint, chromate based. However, new two-part epoxy primers are now better.
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I concur. I think the 2 part epoxy primer we use at work is a Sherwin-Williams product. Works good.
 
Ray Eaker said:
IMO, two part epoxy has always been better but grabbing a can of zinc chromate for a quick, small job is what typically happens (if you can find it).
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I make an effort to use the two part as much as I can. It takes a bit longer, but the end result has better sealing and corrosion protection.
 
Oh they exist alright.

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Ray Eaker said:
(if you can find it).
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It's still out there and readily accessible. It's the aerosol version that is getting hard to find. But it's still available too. Need to look at industrial suppliers and not aviation suppliers. Rustoleum has several varieties but only in paint cans. So do a number of other producers. Plus it's still the go to product in iron works.

Super Coropon is still out there but it's been neutered of it's chromate I believe. But it's a bullet-proof primer around heavy fluid areas like hydraulic systems.
 
Zinc chromate is sacrifial. So it wears out. I don't use it. On steel I like powder coat and my coater phosphatizes steel parts during prep. Phosphatizing is a conversion coating. Also known as Parkerizing. Works well. For other parts, like assembled engine cases, mixed steel and aluminum Cub wings, etc, I use VariPrime. No problems that I've discovered.
 
I am rebuilding a Champ right now, and used 3 coats of rustolem almond it coats well resists scratches and Polyfibre will not affect it, I’ve used it on motor mounts and it really does well. Usually gray. Powercoating is a remarkable product, but it hides defects, and welds, you use cromate, or phosphate I like both, and makes inspection much easier. The oldest paint in rustolum I’ve seen is 10 years old. It cleans well, and doesn’t appear to crack for now. All good products, around exhaust you need to baffle the mount or the coating will bubble, just lite sand and repaint, usually an easy repair.
 
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