Rust spots on grp

[EdWingfield]

This was from the residue of metal grinding operations from an upwind boat.

Skippers, what is the best cost-effective product for removal of rust spots?

 

[Tradewinds]

Oxalic acid solution

 

[Momac]

Bar keepers friend power cream removed a small rust stain from a fitting on my boat ........ I think it may well contain oxalic acid . Applied it to the stain and left it to work for an hour. The stain then wiped off easily.

 

[Pinnacle]

Oxalic acid solution

+1

 

[skip50]

Bar keepers friend power cream removed a small rust stain from a fitting on my boat ........ I think it may well contain oxalic acid . Applied it to the stain and left it to work for an hour. The stain then wiped off easily.

Another vote for barkeepers friend (BKF) easily found in supermarkets. Yes it does contain oxalic acid, but is brilliant for the OP's job. The warmer the day the better. Mind you in Plymouth today it was 13 degrees!

Just over two weeks to relaunching, yippee!

 

[bikedaft]

it carries on rusting away to nothing

 

[VicS]

This was from the residue of metal grinding operations from an upwind boat.

Skippers, what is the best cost-effective product for removal of rust spots?

Oxalic acid, Y10, barkeepers friend or anything else containing oxalic acid will quickly remove the stain...... needs a warmish day though IIRC

Hydrochloric acid will do it, phosphoric acid, limescale removers in general will do it


BUT if hot sparks from grinding are the culprit the little steel particles will have embedded themselves into the surface and will continue to rust and recreate the surrounding stain until they've rusted away themselves. Keep you chosen cleaner handy you may need it again.

 

[NickC]

Oxalic acid solution

+1

Buy oxalic acid powder, mix with warm water as directed on internet for a fully saturated solution. Wear gloves & glasses and keep it off your skin.

 

[Hadenough]

+1

Buy oxalic acid powder, mix with warm water as directed on internet for a fully saturated solution. Wear gloves & glasses and keep it off your skin.

8 posts and no one has suggested suing, progress!!

 

[Bandit]

Y 10 Oxalic acid in a gel .

If its from a boat near by I would notify the owner and contractor of the problem.

To burn in to gel coat needs to be hot when it lands so very close.

With old un polished gel coat a piece of ferrous dust will rust and the stain will get into the porous gelcoat surface.

If it has recently been waxed you may be able to wash it off.

Firstly try washing off boat with detergent and fresh water.

Then try using Y 10, btw oxalic acid will remove wax, wash off with fresh water after a reasonable period.

 

[EdWingfield]

Thanks for the tips boys.

Now the story. Last summer I'd entered a marina (I won't reveal the place, you'll see why later) and was told which berth to take. I went ashore to be a tourist. On return a nearby yottie told me to look at my deck. He said the dust was metal grindings blown downwind from nearby fishing boat maintenance. It was not just my boat affected, but I was closest.

I spoke with the marina manager, we walked to the boat to examine the problem. After a minute he asked me to delay departure for 24hrs to give him chance to fix it. We agreed. I mentioned that there was a conflict of operations ie. fishing boat maintenance next to marina. He wholeheartedly agreed, he said he thought the issue had been resolved in a recent Harbour Users recent meeting - but obviously not. A marina lad got to work on the boat. Next day, after an inspection the Manager asked for another day. I agreed. I said I'd worked in ship maintenance yards for 20yrs and stupid things happen! He thanked me for understanding. The following day's inspection showed the boat to be acceptable. He said the whole stay was gratis, inc free leccy. We parted friends. I see now I should've asked for a small pot of anti rust product as more rust has 'appeared.'

My nearby yottie friend told me there was an upcoming court case between big mobo owner and marina for the same reason ie rust spotting. Yottie friend thought mobo owner foolish as he was not in best of health, had recently lost his wife, and had not asked the marina to rectify the problem. Q. Why take on extra stress?

 

[VicS]

Thanks for the tips boys.

Now the story.

It a well know problem.

Perhaps not these days but back when railway trains had cast iron brake shoes you used to get showers of hot metal particles settling on surfaces near the tracks where they applied the brakes on the approach to stations.
I was called to investigate rust stains on peoples cars parked near a bridge.

Very pleased I was to figure out what was causing it ... until I discovered it was well known!

 

[NickC]

8 posts and no one has suggested suing, progress!!

Was that comment aimed at me by any chance?

 

[Jamesuk]

Oxalic acid solution

Then polish wax it

 

[Marine Reflections]

Personally I wouldn't jump straight in with the oxalic just yet, let me explain.

Ferrous or rusty particles on gel coat should be seen similar to that of a tick - the head is nearly always buried into the skin. The same is always the case with rusty particles, unless of course you happen to see it happening and can remove them before they oxide.
If the particles have been on there long enough for them to turn rusty ( a few days), the chances are they already have a firm hold within the surface.

Now, oxalic will do a good job of making them near invisible and some of the smaller particles will be removed / converted completely, but most will remain, they may be bleached or converted so to speak, but they are still there.

There's two problems with this, firstly they may return as they did in the OP's case, but secondly the particles may get picked up at a later stage when washing or polishing as they are now near invisible. This can cause havoc on the surfaces as you would unknowingly be washing or polishing with a 1 grit in tow.
The head of the particle would rather exchange atoms with the surface than the air, for this reason they embed themselves.

Before I offend anyone with a possible solution that is different, I'd like to say that Oxalic and Y10 will work to a degree, but it usually takes more than one go and comes with the risks of the above.
If however like for me, the job needs to be done in one sitting, removal of the embedded needs to happen before converting / treating what's left.

This is done via a clay bar, a polished blade or even some paper in that order of interference.

A clay bar, when glided over the surface with a little lubrication, will pull the embedded particles from the surface. You would need a firm clay bar rather than a soft one for normal particles.

Of course for this to happen, you need to be able to see where the particles are and if you have converted them before this you won't stand a chance.

Follow this with the converting stages, then as James states - follow with polishing and waxing.

On areas like the non slip or where a clay bar won't work, I would opt for Y10 over oxalic. The reason being, Y10 will absorb the ferrous more into the gel, oxalic will just convert.