hi all,
A while ago a boatbuilder bloke I know suggested Oxalic acid to clean up rust stains on my SS fittings an deck. Tried it and it worked a treat.
Its particularly good for all stainless stuff as well as rust stains on GRP, etc. It's the only cleaner I use now.
Bunnings sell it as Diggers 2kg Rust & Stain Cleaner for $30. You may be able to get it cheaper at house paint outlets. It's a powder and makes up 20 litres @ 100gm/l mixture.
Try it, you won't be disappointed - remember to hose it off with fresh water when done.
regards to all
allan
+1 for Oxalic
After trying all sorts of things to freshen up the 40 year old gelcoat on the lining of my boat, I finally tried oxalic acid and it has done wonders.
And it's great that it is so cheap - just don't buy it as a branded cleaner (Startbrite etc), you'll pay 10 times as much!
A word of warning though - it can be mighty uncomfortable to breath the fumes, especially if you spray it as I did. An ordinary dust face-mask works fine.
Cheers, Graeme
Select to expand quotewongaga said..
+1 for Oxalic
After trying all sorts of things to freshen up the 40 year old gelcoat on the lining of my boat, I finally tried oxalic acid and it has done wonders.
And it's great that it is so cheap - just don't buy it as a branded cleaner (Startbrite etc), you'll pay 10 times as much!
A word of warning though - it can be mighty uncomfortable to breath the fumes, especially if you spray it as I did. An ordinary dust face-mask works fine.
Cheers, Graeme
So you can use it on the gelcoat?
I've read good things about oxalic acid as a cleaner, but not sure with aluminium toe rails, particularly if the anodising is scratched that will allow corrosion of the aluminium. Hard to find a definitive answer whether diluted oxalic as a deck wash will harm aluminium toe rails.
Last time I tried to buy oxalic acid Bunnings were out of stock, and had no idea when they would be able to re-stock. The manufacturer Diggers the same. There were some weak timber cleaner versions available. Has anyone bought it lately?
We used to use it as a brightener on teak decks on the yachts i worked on as a quick fix sometimes rather than use the 2 part teak acid.
Aldi's patio cleaner contains oxalic acid and works well. The Bunnings patio cleaner is supposed to be good as well. If you want the oxalic acid to stay on the hull sides longer then it's suggested to mix the powder with wall paper glue, I have not tried it personally with the glue.
How is it from a environmental view?
Can you spill some and doesn't ruin the harbor?
Be very careful using oxalic acid. Rubber gloves, goggles, long sleeves and pants. It can be absorbed through the skin and it will mess with internal organs.
Environmentally?? If you are on a swing mooring affected by tidal flows and you hang a heavy hessian bag with powder oxalic in it from your bow, I think your bottom barnacles will run for cover.
From Wiki
Oxalic acid in concentrated form can have harmful effects through contact and if ingested; manufacturers provide details in Material Safety Data Sheets (MSDS). It is not identified as mutagenic or carcinogenic; there is a possible risk of congenital malformation in the foetus; may be harmful if inhaled, and is extremely destructive to tissue of mucous membranes and upper respiratory tract; harmful if swallowed; harmful to and destructive of tissue and causes burns if absorbed through the skin or is in contact with the eyes. Symptoms and effects include a burning sensation, cough, wheezing, laryngitis, shortness of breath, spasm, inflammation and oedema of the larynx, inflammation and oedema of the bronchi, pneumonitis, pulmonary oedema. In humans, ingested oxalic acid has an oral LDLo (lowest published lethal dose) of 600 mg/kg. It has been reported that the lethal oral dose is 15 to 30 grams. The toxicity of oxalic acid is due to kidney failure caused by precipitation of solid calcium oxalate, the main component of kidney stones. Oxalic acid can also cause joint pain due to the formation of similar precipitates in the joints. Ingestion of ethylene glycol results in oxalic acid as a metabolite which can also cause acute kidney failure.
Do not become careless or blasé around this product, it can kill you.
I think its fairly safe if you use the product already incorporated in an off the shelf cleaner like a patio cleaner. There is no need to get your hands anywhere near it. I rinse mine off by just tossing buckets of seawater over it.
I should add here too that the performance of oxalic acid is very dependent on ambient temperature. It's not very effective during cold weather. Add warm water to the product and use on a warm day.
I guess I should have said I use disposable gloves, use it in open spaces, wear eye protection, rinse off thoroughly with fresh water, etc, etc.
But doesn't everybody....? 
I got in trouble yesterday for rinsing my paint brushes out in the car park.
Told i should do it in the sink....paint is bad for the earth/dirt.
I delivered the appropriate two word reply.
Its only a amount of time antifoul is banned...imo
