Best way to treat rust under a chrome fender?
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    Senior Member Olivier's Avatar
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    Best way to treat rust under a chrome fender?

    Today I received my CB750 fender to install on my nighthawk (hopefully!) . It's got some amount of rust on the underside (I mean the part exposed to the crud the wheel will be throwing all over it). I removed as much as I could with a wire brush but I'm wondering how to 'stabilize' it so that it doesn't rust further under regular use. I have some gray rustoleum I used on the underside of my muffler pipes because it was very corroded in that area, would it be OK to also use it on the underside of the fender? What do people typically do?

    For the most part, especially the exposed parts, it's in good shape with very little rusting, just some pitting that you have to look at very closely to see, I'm hoping to clean some of it up with a product I have that's usually pretty efficient on my exhaust (can't remember the name). It'll do for now, it was relatively inexpensive and since I don't yet know exactly how I'll mount it...
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    Senior Member 76TWIN's Avatar
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    Only way is to paint or clear coat it. But even then there's no telling how long that would last given all the crap that gets thrown into it from the wheel.
    I don't really bother with it on mine.
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    Senior Member 83XLX's Avatar
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    Yeah, I'd lightly sand it, spray some self-etching primer on it, and then paint the underside either light gray or flat silver.
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    Senior Member Olivier's Avatar
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    Quote Originally Posted by 83XLX View Post
    Yeah, I'd lightly sand it, spray some self-etching primer on it, and then paint the underside either light gray or flat silver.
    Not that I'm trying to be lazy or difficult but I'm a little reluctant to get products that I'll most likely only ever use once. Do you think the self-etching primer is necessary? What does it do? Or straight rustoleum (couple coats) would be enough? It's that one (I got it to coat the underside of my exhaust pipes - not exposed to the public view, basic, flat gray, it worked pretty well). Very basic flat gray color... sanding is done.
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    Senior Member Alan F.'s Avatar
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    Sand or wire brush off as much loose rust as you can, then apply simple White vinegar from the kitchen and add a little scrubbing with whatever you like to scrub with, the 5% acetic acid in the vinegar will convert iron oxide into soluble salts that can be washed off with tap water.

    After plenty of rinsing, dry the fender off with clean towels or rags, leave it out in the sun, etc. Clean with prep solvent or brake cleaner, etc and prime with self etching primer, it's always a good choice and you'll never regret having the unused quantity handy when you want to paint a bike part.

    Self etching primer will essentially help your paint of choice to stick better to the part you're painting, instead of having it easily chip or flake off in subsequent weeks or months on it's own.
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    Senior Member singletooth's Avatar
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    Quote Originally Posted by Olivier View Post
    Not that I'm trying to be lazy or difficult but I'm a little reluctant to get products that I'll most likely only ever use once. Do you think the self-etching primer is necessary? What does it do? Or straight rustoleum (couple coats) would be enough? It's that one (I got it to coat the underside of my exhaust pipes - not exposed to the public view, basic, flat gray, it worked pretty well). Very basic flat gray color... sanding is done.
    your reply as to what does etching primer do:

    Etching primer uses a chemical (acid) to adhere to the metal. Etch primer cures faster. It's a mix of phosphoric acid and zinc. It does, however, prevent the rust problem from worsening. If you go this route you won't have to worry about it again.
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    Supporting Member Yendor's Avatar
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    Wood Bleach.

    Best way to treat rust under a chrome fender?-woodbleach.jpg

    It is basically Oxcalid Acid which loves to attack RUST but will not harm the chrome.

    Mix it up in a Plastic Storage Box that will hold at least 1/2 of the fendrer under the mix level.
    Allow it to soak for a full day srub it with a brass brush repeat as needed.

    Then coat the underside with Eastwood Rust Encapsulator
    https://www.eastwood.com/ew-silver-r...-15oz-aer.html
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    Senior Member Bill H's Avatar
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    Eastwood has several products you can use to coat and stop rust.

    if you use etching primer use a paint fume mask. Its nasty stuff. I never used one till I used etching primer . Now I use one every time I paint.

    Bill
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  10. #9
    Senior Member mike in idaho's Avatar
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    Phosphoric acid, as is found in Coca Cola, and a ball of aluminum foil:
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    Supporting Member krukster86's Avatar
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    I used the above method on the exterior part. I didn't give a damn about the underside, as all sorts of crap is going to accumulate there anyway.
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