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Thread: Steel Surface Coatings

  1. #1
    I'm wondering if there are surface coatings to rust-proof and beautify steel parts of the car that I don't know about. Here are the pros and cons of what I do know (feel free to correct/inform me).

    1. Paint (from a aerosol can or a spray guy). Pros are that it looks good intially and is cheap. Cons are that it isn't that damage tolerant (we tend to paint car parts black and they get scratched up with each rebuild).

    2. Powder coat (baked on). Pros are that it looks good and is very good about not getting scratched up. Cons are that is is difficult to remove to weld-on extra tabs, and impossible to spot repair. It is also more expensive because we have to send parts out to be powder coated.

    3. Black Oxide (like the nuts and bolts that you buy but slightly nicer and more uniform.) Pros are that it is thin, and easily removed to weld on extra tabs. You can also easily spot cracks. It also coats both the inside and out of parts as it is an immersion process. Cons are that it must be oiled, and is not truely waterproof. Also it cannot be spot repaired.

    4. Chrome. Hydrogen imbrittlement... I won't consider for a race car.

    5. Nickle. I know little about this one.

  2. #2
    I'm wondering if there are surface coatings to rust-proof and beautify steel parts of the car that I don't know about. Here are the pros and cons of what I do know (feel free to correct/inform me).

    1. Paint (from a aerosol can or a spray guy). Pros are that it looks good intially and is cheap. Cons are that it isn't that damage tolerant (we tend to paint car parts black and they get scratched up with each rebuild).

    2. Powder coat (baked on). Pros are that it looks good and is very good about not getting scratched up. Cons are that is is difficult to remove to weld-on extra tabs, and impossible to spot repair. It is also more expensive because we have to send parts out to be powder coated.

    3. Black Oxide (like the nuts and bolts that you buy but slightly nicer and more uniform.) Pros are that it is thin, and easily removed to weld on extra tabs. You can also easily spot cracks. It also coats both the inside and out of parts as it is an immersion process. Cons are that it must be oiled, and is not truely waterproof. Also it cannot be spot repaired.

    4. Chrome. Hydrogen imbrittlement... I won't consider for a race car.

    5. Nickle. I know little about this one.

  3. #3
    Senior Member
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    Any coating that requires electroplating and some of those that don't have the potential for hydrogen embrittlement. This includes chrome, nickel, black oxide, manganese phosphate, and zinc and probably many others that I'm not familiar with.

    Nickel is usually good for tight tolerance parts that will have large contact stresses. It is extremely corrosion resistant.

    Zinc is good for low tolerance parts that don't have high contact stresses or small deformations don't matter. It has variable corrosion resistance depending on type, yellow, bright, or black.

    Manganese phosphate is like black oxide. All the same downsides and limited upsides. Where I work some people consider one great and the other horrible while others have the exact opposite opinion. In general they both suck in corrosive environments.

    Where I work we pretty much only use paint/powdercoat, zinc, nickel, black oxide, and manganese phosphate on steel. We build aircraft tooling and automation machines that in general end up located in really bad environments, with large ranges of temperature, humidity, and salt in the air.

    A FSAE car during a short life in the Northern half of the US would probably experience similar conditions as would any car that gets shipped overseas. I wouldn't consider using anything other than Nickel or paint/powdercoat on one. Black oxide and manganese phosphate are too time intensive to maintain and pretty much always look as bad or worse than bare steel. Anyplace that I would consider using a zinc plated component is also the same area I would use aluminum or plastic on a race car.
    Josh Gillett
    Oregon State FSAE '04-'06

  4. #4
    Thanks for your imput. I have been building my own FSAE car for two years now (almost done!) and want a bit longer life out of the parts than the typical FSAE team. I plan to powder-coat the frame after driving it a year (to make sure all neccessary tabs are welded on). My question here primarily relates to the a-arms, push-rods and tie-rods where I want to see any cracks, and potentially make repairs.

    I wonder if there is a black variant of nickel. I'm not too fond of that shiny silver look, and it wouldn't fit with my current color scheme.

  5. #5
    Black oxide doesn't prevent rust. Or at least it sure didn't on the black oxide cap screws and allen keys we had.

    You could make a-arms, hubs, etc out of stainless instead of 4130. For the stress levels a FSAE car sees the design isn't too difficult. I'd do that for the a-arms at least, so you can stake spherical bearings or have threaded ends without having to mask crap off when surface treating.

    I dig Nickel plating. There's some way.. might have been called sandy nickel or pearl nickel plating where you can get a nice satin finish, looks almost dull and rustic. I really dig it.

    With Nickel I believe you can do a post-process bake on the part for Hydrogen relief. Did that on my uprights one year.

  6. #6
    Black oxide is more a rust inhibitor than a end all rust preventative. I'm not sure why the comment was made that black oxide takes a long time. The only thing that takes a while in the process is getting the dip tanks up to temp. After that it only takes a couple hours from start to finish.

    I am a big fan of the process and to say that it "pretty much always look as bad or worse than bare steel" completely confuses me. Provided the parts had a good finish on them before going in the tanks, our parts always came out nice. Cleanliness is very important.

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