Ingrained Rust Stain Removal?

Richard10002

Richard10002

Well-Known Member
Joined
17 Mar 2006
Messages
18,979
Location
Manchester
Visit site
Have just removed the diaghram shower pump from the aft heads because its' base is rusty and we get rusty water seeping onto the shower floor for a while after a shower is finished. not sure if it was the pump leaking, or just water getting around it, sitting in the rust, (making it rustier), and then making its way out as the boat moves about.

This has been going on for years I would guess and, having removed the pump, there is an apparently ingrained rust stain under and around where it was:

IMG_0002.jpg


When I say ingrained, I suppose it hasnt become part of the gelcoat, but's stuck pretty firmly to it.

I've tried 2 goes with Oxalic Acid, (Gel Kleen), leaving it for a few minutes as per the instructions and the result is as above.

Can I leave oxalic Acid overnight, or could it do some harm, or has it done what it can?

Any other suggestions?
 
Yes leave the oxalic acid for longer. I don't believe it will harm the f/g.
You might consider one of the rust converters (phosphoric acid I think ) and keep trying. olewill
 
Yes leave for longer. Scrub it about a bit as well every so often.

I dont know the concentration of oxalic acid in Gel Kleen. A more concentrated mix of oxalic acid and wallpaper paste might be more effective. As William H suggests a phosporic acid rust remover might be effective.
 
I wouldnt use a pan scourer - you will remove the gloss finish and any chance of keeping the area shiny clean. Instead, use a wide flat wood chisel as a scraper to remove any rust flake (as opposed to stain) from the surface. Oxalic acid will deal with stain but my guess is that you have a layer of solid rust left behind.

And try to get some oxalic crystals rather than the fairly dilute proprietary compounds.
 
Be careful with Phosy Acid ... it is not one to leave working for too long ... better to do it in stages ... apply, scrub with non-scouring pad, rinse of ... repeat etc.

Phosy acid is a combination of Sulphuric acid and phosy rock .. a brilliant stain remover on ships paintwork - but it destroys any gloss finish sometimes easier than the stain ...
 
As Vic suggests a poultice of oxalic and wall paper paste applied (I would also add a bit of washing up liquid to improve wetting property),it also helps to lay it on thick and then cover with cling film/poly bag so that it doesn't dry out.
Never had to tackle such a bad stain on F/glass but the cling film poultice worked a treat on rust stained blockwork on drive.
 
Still better than leaving a nasty brown rust stain. And yes it may remove some of the shine but that can soon be put back with some rubbing compound (Farecla G10) and a decent polish.
 
[ QUOTE ]
Be careful with Phosy Acid

[/ QUOTE ] I don't know what you are calling "phosy acid" or "phosy rock"
Will. H referred to phosphoric acid. Phosphoric acid is phosphoric acid, H3PO4, AKA orthophosphoric acid. It does not contain sulphuric acid.

Phosphoric acid is however a strong acid, like sulphuric, hydrochloric and nitric acids, and should be handled with the same care although it does not produce fumes like hydrochloric and nitric acids, is not a strong oxidising agent like nitric acid, or a powerful dehydrating agent like sulphuric acid. For the suggested use I would use a dilute solution ( 5%, 10% ??).

I would be wary of using some of the rust converters without testing a small patch first just to be sure that the rust stain is removed and not merely "converted" to something just as bad!
 
[ QUOTE ]
[ QUOTE ]
Be careful with Phosy Acid

[/ QUOTE ] I don't know what you are calling "phosy acid" or "phosy rock"
Will. H referred to phosphoric acid. Phosphoric acid is phosphoric acid, H3PO4, AKA orthophosphoric acid. It does not contain sulphuric acid.

Phosphoric acid is however a strong acid, like sulphuric, hydrochloric and nitric acids, and should be handled with the same care although it does not produce fumes like hydrochloric and nitric acids, is not a strong oxidising agent like nitric acid, or a powerful dehydrating agent like sulphuric acid. For the suggested use I would use a dilute solution ( 5%, 10% ??).

I would be wary of using some of the rust converters without testing a small patch first just to be sure that the rust stain is removed and not merely "converted" to something just as bad!

[/ QUOTE ]

Catch this .....

Quote "PHOSPHORIC ACID
The large percentage of the phosphoric acid in fertilizer phosphates is produced from sulfuric acid and phosphate rock. This phosphoric acid, known as "wet-process" acid, is then used in the manufacture of triple superphosphate, ammonium phosphates and other high analysis fertilizer products.
The primary chemical reaction in the production of wet process phosphoric acid is between the calcium phosphate constituent of the phosphate rock and sulfuric acid to form phosphoric acid and calcium sulfate. The principal difference in the processes used throughout the world is the degree of hydration of the calcium sulfate, which can be varied by changing the temperature and P2O5 concentration in the reaction. The most popular process which is used by the Florida producers is known as the dihydrate process in which gypsum is precipitated.
Phosphoric acid production by the wet process requires three main operations: reaction between the phosphate rock and sulfuric acid, separation of the gypsum from the phosphoric acid and the concentration of the phosphoric acid to the desired P2O5 level. The production units include large reaction vessels where finely ground phosphate rock (dry or wet slurried) is first treated with weak phosphoric acid and then reacted with approximately 55% sulfuric acid. Additional process efficiencies and proper acid concentrations. The calcium sulfate is then separated by vacuum filtration and washed for optimum recoveries of phosphoric acid. Various concentrations of phosphoric acid are produced from the filtration operation with the weak portions being recirculated for proper process controls and the end product containing usually 28 - 32% P2O5. In the final step, the filtration product is concentrated under vacuum and with heat to the desired P2O5 level, depending upon the specific end use, with the highest concentration normally being 52-54% P2O5. This concentration is also used for acid shipped for fertilizer usages." Unquote

Cut and pasted from : http://www.afpc.net/phosphoricacid.html

I worked on Bulk Acid Ships around UK / North Sea carrying High concentrate Sulphuric Acid to receivers such as Pfizer, Shell Chemie, etc. to use in production of Phosy Acid .....
Carried High concentrate Phosy acid and believe me the sulphuric acid stink is VERY strong !

I've even carried it for Turkish Military ......

OK - the above cargoes are serious acid level cargoes and not for casual work. The Phosy available to general public is well diluted unless you have access to industrial supplies.
 
Since you've tried the obvious (Oxalic Acid) I'd put a polishing head on an electric drill and polish it out with paste. You'll find a polishing head handy to have for odd nooks anyway. I don't like to carry too many different chemicals on board in case they should ever combine accidentally or leak somewhere. Mrs L accidentally put a bottle of bleach (hypochlorite) down in the kitchen area the other day, on the carpet, and there was enough on the base of the bottle to bleach a nasty ring. Irreparable /forums/images/graemlins/frown.gif
 
Thanks to all -

Not too worried about losing the gloss on the F/G - it's hidden under the handbasin behind a door and, having lived with a rust stain and pump for over a year, a loss of gloss would be a minor detail.

So far I've left the GelKleen on overnight and it has worked to a degree. I think what is left is a thicker layer of rust which might scrape/polish off before using the oxalic again. I've got a dremel with a fair few attachments, so something should work.

I think I'll steer clear of phosy acid in the short term.

Thanks for all the help - So far so good, but not the quick job it should have been, (is it ever?? (: ).

Richard
 
The grp restorer i mentioned in other thead will remove it.

Actually, oxalic *will* remove it but it needs to be really violent contrated gear, not weedy y10 cack that is so rubbish you can put it in sandwiches.
 
[ QUOTE ]
Catch this .....

[/ QUOTE ] All jolly interesting but no relevance to the use of phosphoric acid based rust removers or to pure phosporic acid solutions either.

Any strong odours or fumes you may have experienced would have been due to imputities in crude materials as both phosphoric and sulphuric are odourless when pure. I can imagine that either of the common phosphate rocks, apatite or chlorapatite, will produce an unpleasant mixture with concentrated sulphuric acid as they are in effect mixtures of calcium phosphate with calcium fluoride and calcium chloride respectively. If HF is released from the former then it would be very unpleasant to say the least.
 
Sorry Vic ... but years of carrying the stuff .. working with it ... technical vs practical are vastly different.
 
Not sure about Malta, but the Med in general has ironmongers and supermarkets that sell stuff you wouldn't be allowed to use in UK...try looking for "desrusticant" - a reddish liquid. Doesn't say what it is on the plastic bottle, but it does the trick. It can bleach white grp so do the whole panel and no-one will notice.
 
[ QUOTE ]
Not sure about Malta, but the Med in general has ironmongers and supermarkets that sell stuff you wouldn't be allowed to use in UK...try looking for "desrusticant" - a reddish liquid. Doesn't say what it is on the plastic bottle, but it does the trick. It can bleach white grp so do the whole panel and no-one will notice.

[/ QUOTE ]

Bit like here where they undiluted stuff that you have to dilute 10 - 1 to get spirit vinegar suitable for your chips ! Not uncommon for people to be taken to hospital with burnt throats .. stomach troubles after mistakenly using it undilute ...

Works wonders on blocked waterways ! Just have to make sure you flush out well after !!
 
I expect the earlier sugestions will do the trick. If however they do not and the marks really get to you. Then you could always resort to an angle grinder with a heavy duty sanding disk. This would be sure to remove the stain and some of the gelcoat. Then you would have to do a gel coat repair job.
 
You must log in or register to reply here.

Share this page

Top