Ospho question

rrman61 · Aug 23, 2018

When using ospho (spelling?) or similar rust converter on light surface rust,should the surface be wire brushed clean before painting? It's on a redecked bush hog in humid conditions.

Janicholson · Aug 23, 2018

Only loose rust should be removed. Shiny steel has no chemical reaction with the product. Without the reaction, it can just fall off. If patchy rust, just treat the rusted areas. A finish must be applied over the product because they are not very UV resistant and will decompose in sunlight. Jim

ss55 · Aug 23, 2018

Is that a phosphoric acid rust converter? They work well. Check the directions, many say remove the loose rust before applying.

When you are done, consider painting the entire underside of the deck with a graphite paint to reduce the amount of grass that sticks to it and also make it easier to clean out.

MarkB_MI · Aug 23, 2018

What I've done is to wire-brush first to remove heavy rust and loose paint. Ospho likes to have a little rust to react, but it will work on bare metal. Then let it dry THOROUGHLY. The result will be fairly rough at that point, with drips and runs and paint and maybe still some bare metal. I lightly sand it to remove the rough spots, then re-apply. You can do this as many times as you have patience for, but a couple of coats should be enough for your purposes. Lightly sand one last time before painting.

Mike M · Aug 23, 2018

The guys on here seem to think it works ? But from a few times I've tried it on some touch up spots on cars it was worthless ! Just dabbing on paint held up as good ( which isn't good ) without using that stuff.

Glen SW Wi · Aug 23, 2018

Used more gallons of it than I care to remember when I worked on an offshore oil production platform out in the Gulf. Chip off the loose rust first. Nothing like salty sea air to make rust. It worked great for us. Have part of a gallon in the garage right now. It is phosphoric acid which turns iron oxide into Iron phosphate.

showcrop · Aug 23, 2018

To answer your question rrman61, you don't need to wire brush AFTER, but, understand that there is likely to be some residue of excess Ospho, that may not be a good surface for your primer to grip. after the treatment time, before it is thoroughly dry, I toss the parts in water in order to rinse the excess off, and larger pieces get pressure washed.

Ospho question

rrman61

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Janicholson

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ss55

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MarkB_MI

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Mike M

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Glen SW Wi

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showcrop

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