What acid for cleaning rust off paintwork ?

[ribbony]

Oooops, got some rusty bits of metal grindings to get off the paintwork. The nice white enamel (single pack) had some fine bits of metal embedded in it form some past grinding. We usually get it all off soon after grinding but we somehow missed this somehow, only to discover it after 5 mths absence from the vessel in winter.

We have used both phosphoric and hydrochloric on seperate occasions to remove similar stains from old paintwork that we knew we were going to sand off latter. Now we have our nice new paint work and are a bit more tentative about what acid to use, if any. Oxalic is not strong enough to do the job.

I doubt either may eat the coating off the vessel, but we do not want to end up with chalky paint surfaces afterwards.

Any suggestions appreciated.

[cooper]

...sorry no suggestions...if it has melted into the paint work its a ....

(by the way) how soon till you cast off for the wide blue yonder ?...

[donradcliffe]

I have good luck with Oxalic--just did the same job yesterday to clean up where I had to saw through an anchor chain (long story). I bought the oxalic acid as crystals in a hardware store (cheap) and mix with warm water to make a solution.

Looked at my neighbor's fancy boat cleaner and it was a mix of oxalic and phosphoric acid.

[Vasco]

Oxalic acid will do it. If you can get your hands on something called "Barkeepers Friend" which is a white powder, you'll find that this is the best for that kind of job. I had little rust spots on my swim platform from filings and they all came off with this product. Much better than that FSR gel which is also oxalic acid.

[AnchorageGuy]

we have used a product from Home Depot called Rust-Aid with great success and won't hurt paint, etc.

[JusDreaming]

Whink Rust Stain Remover works really well for us

[ribbony]

Thanks everyone. We will give the oxalic a try. We have a tub of crystals from our old GRP boat, we used it for stain removal from the sails and some deck stains. I can not say it removed much, but then we were trying not to dissolve the sails and would of diluted it substaintally.

Hopefully the metal has not melted into the paint, as it was stray dust that got in under the canvas tarps we used to protect the deck and should not have been a direct hit from grinding sparks.

As for how long till we sail off into the Big Blue, well our estimations on that have been so far off to date. When we bought the project I thought it was going to be 3-4 mths to sailing, it has been 2.5 years and perhaps now it is 3mths till we can do some serious sailing. Our goal at the moment is to be able to hoist some basic sails and get up to Sydney harbour for the NYE fireworks. It is not that far from us but we have to go out the heads, up the coast 20km and into Sydney Harbour and we do not want to only do it on the motor without some sails as a back up. It will be close but I think we can achieve that. Thanks for all the support, there is light at the end of the tunnel