Rust prevention inside panels.

Discussion in 'Chassis restoration' started by PeterRomvig, Sep 13, 2020 at 9:53 AM.

  1. PeterRomvig

    PeterRomvig Well-Known Member

    Finally I'm getting ready to tackle the last of all the rust in my 70 GS before paint. I will be replacing rear outer wheel wells, trunk floorpan drop panels, quarter panel skin, trunk filler panel under the rear windshield, drip rails ect. Also i will be deleting the vinyl top because of all the rust and moisture damage underneath. One question came to mind! What are a good way to tackle surface rust inside crevices and cavities. I was thinking about making a 20-30% phosphoric acid solution and spray it with a weed sprayer and then let it dry, epoxy over where i can get to and 3m cavity wax where I can't get epoxy over. Thank you.
    Last edited: Sep 13, 2020 at 1:50 PM
  2. 12lives

    12lives Engage! - Jean-Luc Picard

    You have to neutralize the acid after the rust is converted. Other wise you are looking at corrosion in the panels later. I would simply use a rust sealer paint (POR 15 or other) over the rust. Inside cavities I would use a Eastwood or other spray sealer: IMG_20200830_141107_996.jpg
    Last edited: Sep 14, 2020 at 10:32 AM
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  3. wkillgs

    wkillgs Gold Level Contributor

    Phosphoric acid doesn't need to be neutralized. It's a common ingredient in metal conditioners. It will form a phosphate coating that some primers won't adhere to.... it depends on the primer.
    It can be rinsed off with water after an activization period of a few minutes if you want to minimize coating buildup before painting.
    There's a product called Picklex that contains Phosphoric acid. Some guys on the forums swear by the stuff.... use it to neutralize the rust and apply primer over it.

    IMO your plan will work fine, may even be overkill for a garage kept car.
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  4. PeterRomvig

    PeterRomvig Well-Known Member

    Thank you, I guess your right about it being overkill when sitting in my heated garage with the a/c on most of the time! It's just for that extra peace of mind knowing i did something
  5. 12lives

    12lives Engage! - Jean-Luc Picard

    This is what I was reading: "After completion, remove any excess or non-converted (SEM) Rust Mort by rinsing with water and a brush. Make certain all surfaces are completely dry before proceeding with body filler or primer per manufacturer’s recommendations. Failure to remove excess material can result in loss of adhesion of subsequent top coats. Limit exposure after drying the surface to eliminate flash rust." and "Rust Mort is not designed for prolonged exposure and must be rinsed, dried and topcoated. Use care to keep Rust Mort off painted surfaces as it may react or discolor top coats or undercoats."
    I thought it was to remove excess, non consumed acid. Rust Mort contains Phosphoric acid.
    "Picklex® 20 is the only pre-treatment (conversion coating) which can be brushed on a metal surface at room temperature without rinsing and completely removes the oxidation from the metal surface, provides a Conversion coating, Seals the coating and stops the oxidation process, all in One Step." and "Even there is a small amount of Phosphoric acid as an ingredient, the final product is water based, water soluble and non-hazardous in nature"
    So it depends - Rust Mort contains up to 60% acid. Picklex contains less than 7%. Then there are folks who buy food grade Phosphoric acid and mix their own. I would be careful using high levels of acid in seams. Same thing with paint stripper. My 2 cents.
    Last edited: Sep 14, 2020 at 10:29 AM
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