Rust stains on fiberglass-what works?

The classic remedy for rust stains is oxalic acid.

Most hardware stores do not carry oxalic acid, but plumbing supply houses are more likely.

Oxalic acid really is poisonous (it isn't just nanny state fearfulness), so handle with care.

Joe Gwinn

First, give the "Mr. Clean Magic Eraser" a try--I dunno what's in it and it's a bit abrasive, but the things are amazingly effective on a wide range of crud. If that takes your rust stains out you're done.

If it doesn't, try oxalic acid in some form (chemically, oxalic acid reacts with rust to form water-soluble compounds that can be washed away)--"Barkeepers Friend" and "Zud" are two reasonably available (in the US anyway) brands of scouring powder with oxalic acid--both are abrasive though, Zud more so than Barkeeper's Friend. Any decent paint store should have some brand or other of "wood bleach" or "wood brightener", which are also mostly oxalic acid without the abrasive. You'll need to give it some elbow grease and maybe some assistance from a Scotchbrite pad.

If those don't take it out it's probably not coming out other than by sanding away enough gel coat to get below the rust layer.

Once you've got the rust stains out, if you want a shiny surface go over it with some polishing compound.

On the other hand, Barkeepers Friend contains enough Oxalic Acid to do the job. It's readily available at most grocery stores.

Zud is another cleaner that contains oxalic acid.

EvapoRust works great on rusty metal, wonder if it would work on rust stains?

----- Regards, Carl Ijames

BarKeepers Friend....

Also works GREAT on stainless... We use it to polish the tank on our tanker. Use it and a window scrubber to do larger areas.

On Sat, 10 Jul 2010 08:02:57 -0700, JR North wrote the following:

Oxalic acid (aka "Deck Brightener") is one method. Neutralize with salt water.

Oxalic acid (as L Jacques suggested) is good. It dissolves ferrous metal as well as rust, you must rinse it away or the iron comes out of solution when it dries and the stain is back.

Mix with water in a plastic bucket, do NOT get in contact with any iron tools, not even a paintbrush ferrule. Some paper waste on the stain will hold the liquid while it attacks the stain.

Some of the boat people recommend "Lime-a-way". I believe that it is made for use in cleaning stains from fiberglass showers and tubs. They recommend following the instructions on the label so apparently it is strong stuff.

Cheers,

John D. Slocomb (jdslocombatgmail)

Yeah, it's irritating. So is vinegar, or pepper... that just means you won't accidentally ingest any and remain unaware. LD50 in rats is 9.5 ml/kg of strong water solution (so avoid drinking a pint of the cleaner after you get it mixed).

It's relatively benign stuff. It's the reason rhubarb is unpalatable until cooked.

I saw a rack of it at Lowe's this weekend.