Removing rust with Hydochoric Acid

jac

jac

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the drain from my Anchor Locker has left lovely brown stains on the gelcoat which I expect is primarily rust mixed with any bits of organic detritus that have ended up in there. I have some brick cleaner which is basically HCL. Does the panel think this will be ok to remove the stain. I know Oxalic acid is the usual suggestion but iirc HCL is used commercially to remove rust and for cleaning and I don't want to go and buy effectively a duplicate product.
 
It will dissolve rust OK but you will find a gel such as Y10 more convenient to use and if this will be a recurring problem handy to have.
 
When I was a young lad I worked in a lab that carried out water contents on bitumen emulsions. A long row of glass condensers was fed by water that came through the factory in steel pipes, so they became very rusty inside. The highlight of my week was every Friday afternoon, sucking HCl through them using a vacuum pump, which in less than a minute restored them to perfect cleanliness.

Chris Beeson in April's YM looked at methods of removing rust stains from sails. HCl was probably the best, just a few seconds of soaking removed all traces of rust.
 
Vyv

What do you think about using Hydrochloric Acid on rust spots on a steel deck to clean the steel before repainting and what would you use to remove the Hydrochloric Acid in preparation for painting.
 
Hidrochloric acid is perfect for regular steel but never use it for stainless steel as it makes it more prone to further corrosion,use nitric acid for that.
 
Rogershaw said:
Vyv

What do you think about using Hydrochloric Acid on rust spots on a steel deck to clean the steel before repainting and what would you use to remove the Hydrochloric Acid in preparation for painting.
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Hydrochloric acid would certainly work in this way, although my knowledge of steel boats is limited and there may be better ways. Any base would neutralise it but garden lime is probably the best combination of availability and cost. A hose pipe would seem like a pretty effective removal method but I guess some acid might remain in pits and crevices.
 
Thks Vyv
Its where damage and cracking of the paint has allowed rust to get under the paint. I plan to grind/sand the paint to expose all the rust but have found that unless I grit blast that I cannot do in my marina some rust still stays even using rust converter. So was thinking of using pool acid (HCI) to clean the remaining bits of iron oxide then rust converter then paint like epoxy or hammerite
 
Rogershaw said:
Vyv

What do you think about using Hydrochloric Acid on rust spots on a steel deck to clean the steel before repainting and what would you use to remove the Hydrochloric Acid in preparation for painting.
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25931 said:
Just hose it down.
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Rogershaw said:
Thks Vyv
Its where damage and cracking of the paint has allowed rust to get under the paint. I plan to grind/sand the paint to expose all the rust but have found that unless I grit blast that I cannot do in my marina some rust still stays even using rust converter. So was thinking of using pool acid (HCI) to clean the remaining bits of iron oxide then rust converter then paint like epoxy or hammerite
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The trouble will be that after cleaning with HCl the steel surface will rust again very quickly. Id use phosphoric acid and carefully rinse away excess aiming to leave a surface protected by a phosphate film
 
VicS said:
The trouble will be that after cleaning with HCl the steel surface will rust again very quickly. Id use phosphoric acid and carefully rinse away excess aiming to leave a surface protected by a phosphate film
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Great idea Vic , I just need to find where I can get a small quantity of phosphoric acid in South Africa from.
 
Liquid rust stopper aka phosphoric acid has many commercial names but its freely available from car bits shops. Theclayer it passivates is soft, easily worn through so you have to paint it after killing the rust. Also for the ultimate anti rust paint have a look at zinc chromate. Its usually a weird duck egg green colour, goes on like gloss metal paint, but is the best anti corrosion paint available. Used with structural steel in buildings a lot, its also pretty cheap for Building use. Takes several days to dry. You might use the laqueur type textured paints, though good, not as good as zinc.
 
We used brick cleaning acid - largely hydrochloric - to resurrect a cement mixer that had got a bit crusty. It was painted on, then hosed off. It did a great job, but we noticed that, forever after, the mixer was prone to rusting, even where it had been repainted.

Does anyone know - Can the chloride element of the acid have the same affect as salt water? Is it an urban myth that these ions can get in to the structure of the steel and continue to cause rust? Certainly the empirical results weren't good.
 
> Removing rust with Hydochoric Acid

Use Muriatic acid which is watered down Hydrochloric acid it's safer and will remove rust stains. For any rust on steel don't use acid grind it to bare metal and put on two coats of zinc rich epoxy paint.
 
KellysEye said:
> Removing rust with Hydochoric Acid

Use Muriatic acid which is watered down Hydrochloric acid it's safer and will remove rust stains. For any rust on steel don't use acid grind it to bare metal and put on two coats of zinc rich epoxy paint.
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Muriatic acid is merely an old name for hydrochloric acid. No reduced concentration is implied. It is a solution of hydrogen chloride ( a very soluble gas) in water and available in concentrations up to around 36% by weight.
 
jac said:
Just as an update.

Used the brick cleaner which is basically HCL.

Rust marks came off beautifully. Also removed the stains on the gelcoat around the exhaust.
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coenvanwyk said:
It might work well on glass, but the OP has a steel hull, and HCL on there will cause further rusting. Phosphoric acid is the way to go in that care.
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jac said:
No I have a GRP hull.
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Its Roger Shaw who has a steel boat!
 
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