Black Phosphate Preservation

[Gene M.]

Re: Black Phosphate Preservation

Mike,
I've had many, many replated black zinc chromate, and they are not shiny. The order of difference is no different than urethane base clear coat paint is to lacquer. True, no texture like phosphate but defiantly better corrosion prevention and oil is not necessary. I drive my car a lot and 30 years later hardware with zinc is still good. I don't use repro fasteners, they are junk at best.

On graded hardware you need to request from the plater that they be treated against hydrogen embrittlement.

[Bill L.]

Re: Black Phosphate Preservation

Highly recommend RPM Rust Prevention Magic. Vendors have RPM in stock. About $35.00 shipped.

RPM is an excellent bare metal protectant.

Bill

[Michael G.]

Re: Black Phosphate Preservation

Gene, glad you're getting good results with your zinc plating. I agree that a thick coating of zinc with a good black chromate is better than 1970's phosphate and oil, but, there is no way a normal thickness of zinc on fastener exposed to the elements ever lasts 30 years without significant corrosion. In any case, no matter the chromate, the zinc chromate improvement over phos and oil would never be more than a year or two on a road vehicle.

I've tested more different zinc chromate platings in salt spray, long-term vehicle corrosion durability tests, and every other scenario than you'd ever believe and no zinc chromate lasts remotely that long.

Maybe you had cadmium on your parts, which might last that long, but not any normal thickness of zinc, no matter what chromate you put on it.

[John D.]

Re: Black Phosphate Preservation

A good substitution for black phosphate finish that is far better corrosion protection is black zinc chromate. As it ages the appearance will better replicate black phosphate. My thought is if base clear urethane paint is ok in substitution of lacquer than why not black zinc chromate for black phosphate?

Availability of black zinc chromate at most plating shops is more prominent than black phosphate.

Gene and others. Black phosphate is basically a temporary finish and although we all mean well few actually put an oil and other crap on the bolts. I used to look at 62 to 65 Fis that I restored and was very disappointed to see that the black phosphate fillister screws were rusty.

So I switched to Black Zinc. At first it's too shiny but as mentioned it tones down to a natural look and stays that way. I can't tell you how long but I am watching several restorations I did in 2007 and still no evidence of rust. So I am sticking with the black zinc finish and recommend it to others.
On the other hand the Eastwood satin clear seems to work quite well too. Trouble with coating with oil is the dust sticks to it like glue. John

[Gene M.]

Re: Black Phosphate Preservation

Gene, glad you're getting good results with your zinc plating. I agree that a thick coating of zinc with a good black chromate is better than 1970's phosphate and oil, but, there is no way a normal thickness of zinc on fastener exposed to the elements ever lasts 30 years without significant corrosion. In any case, no matter the chromate, the zinc chromate improvement over phos and oil would never be more than a year or two on a road vehicle.

I've tested more different zinc chromate platings in salt spray, long-term vehicle corrosion durability tests, and every other scenario than you'd ever believe and no zinc chromate lasts remotely that long.

Maybe you had cadmium on your parts, which might last that long, but not any normal thickness of zinc, no matter what chromate you put on it.

Mike, yes they still look good. One note, I don't drive my Corvette in the salt. Most weather is dry except the road tour always gets rain.

John, it sounds as if you are having good results with black zinc chromate also.