Saharan dust stains

[alancollins]

My boat suffered quite badly with yellow stains all over the decks. I made a strong solution of oxalic acid and sprayed this on. A few minutes later I was pleased to see the stains fading and ,after giving the worst areas a second coat, a half hour later the decks were back to their usual whiteness. I hosed the boat off and went home well pleased. Back on board three days later to find the stains were back. Not as bad as before but a pale yellow colour everywhere. No more dust had blown in, the original stains had simply reappeared. I am baffled and would welcome comments from anyone who has experienced the same. Has oxalic acid lost its magic?

 

[TSB240]

My boat suffered quite badly with yellow stains all over the decks. I made a strong solution of oxalic acid and sprayed this on. A few minutes later I was pleased to see the stains fading and ,after giving the worst areas a second coat, a half hour later the decks were back to their usual whiteness. I hosed the boat off and went home well pleased. Back on board three days later to find the stains were back. Not as bad as before but a pale yellow colour everywhere. No more dust had blown in, the original stains had simply reappeared. I am baffled and would welcome comments from anyone who has experienced the same. Has oxalic acid lost its magic?

Phosphoric acid is better often found in diluted form in Cilit Bang extreme grime and grease remover. It is used specifically as a rust converter and is better for removing any iron oxide particles .

 

[alancollins]

Thanks for that. Is the Saharan dust iron oxide? It's certainly the right colour but that never occurred to me .

 

[Graham376]

Sahara sand is a fairly normal event where we are but it washes off the deck without staining but the next rain shower can wash it down from the mast and rigging again. Has anyone been grinding metal upwind from you, surprising how far it can carry and that does stain.

 

[alancollins]

It doesn't look like rust particles and what is puzzling me is that oxalic acid got rid of the stains, but they crept back a couple of days later. When I have used oxalic acid in the past it has proved a permanent cure, but not this time. I need the advice of a chemist!