Removing rust flakes from gelcoat

[EmeraldCoastSailor]

I learned from someone years ago to not cut metal on board if it can be avoided as the tiny metal flakes produced will cause havoc when they rust as it is hard to clean up every bit of . I got as far away from the boat and cut some chain on the dock but stupidly tracked some flakes on board and the wind may have blown some metal on the boat as well (I was using angle grinder so the metal flakes produce were too small to see). Very dumb mistake on my part. Now I have rust marks that appear to be in the gelcoat; boat soap and a stiff brush didn't help much. Most of the damage is done on a non-skid area but a little bit is on a small smooth spot; not sure that is good or bad.

Does anyone have any ideas regarding how I might correct the issue?

[Shenandoah52]

If you're near your boat you could try using a paper towel soaked in vinegar and held down over the gelcoat as a test. It may be all you need. Give it a little time to chemically change the rust. There are commercial solvents (Starbright?) you can buy to do this as well. I use vinegar a lot for this, but that's not a guarantee it will render your gelcoat perfect again. But if you have some vinegar and a paper towel...

[lars]

Bar keepers friend . Walmart or dollar store has it for about 2 bucks

[stormalong]

Go to your local hardware store and buy oxalic acid crystals. Also known as wood bleach. Mix it with water at about one tablespoon to eight ounces. Brush it on your stains and keep it wet with your mix until the rust marks disappear. Rinse with plain water.

You might have to repeat to get it all. Oxalic will also strip wax so it will have to be redone.

This is the same as fiberglass stain remover except FSR is gelled, a much weaker solution and far more expensive.

[roverhi]

Barkeepers friend has Oxalic acid as one component. Oxalic acid really works on rust though it may take repeated applications till all the ferrous material is gond. Paint it on with a brush or rag and wash off before it has a chance to dry. Also a good wood bleach.

Wouldn't mess with Ospho or Phosphoric acid. It converts rust to an oxide that is stable enough to paint but doesn't bleach out the rust stains.

[woc]

Originally Posted by EmeraldCoastSailor

I learned from someone years ago to not cut metal on board if it can be avoided as the tiny metal flakes produced will cause havoc when they rust as it is hard to clean up every bit of . I got as far away from the boat and cut some chain on the dock but stupidly tracked some flakes on board and the wind may have blown some metal on the boat as well (I was using angle grinder so the metal flakes produce were too small to see). Very dumb mistake on my part. Now I have rust marks that appear to be in the gelcoat; boat soap and a stiff brush didn't help much. Most of the damage is done on a non-skid area but a little bit is on a small smooth spot; not sure that is good or bad.

Does anyone have any ideas regarding how I might correct the issue?

West Marine sells a product called “ On&Off” , brush it on the area and the rust spot will vanish, rinse off with soapy water. Works on chrome equally well.

[singlespeed]

On-Off application will require an application of a surface protector as well. It works really well, but don't let the area on the deck sit to long without some protection or it will rapidly acquire stains.

[sail sfbay]

Starbrite Rust Stain Remover

[Greg Mason]

I have used FSR, works well. For more serious stains, like around exhaust outlet, I have used oven cleaner. As with these and other serious products, don't wait long. Much easier to do multiple applications than be sorry.

[Jeanneau 45.2]

Originally Posted by Greg Mason

I have used FSR, works well. For more serious stains, like around exhaust outlet, I have used oven cleaner. As with these and other serious products, don't wait long. Much easier to do multiple applications than be sorry.

+1 for Davis Instruments FSR Fiberglass Stain Remover. May indeed take multiple applications, tooth brush good for applying inside the nonskid pattern.

[wingless]

+1

The product I use for rust stains is FSR. It requires patience and multiple applications, but has always worked in every case for me. I apply, do something else, apply again, repeat, until the problem is gone.

[Captain Bill]

Despite the advice already given, Ospho does a great job of removing rust stains from gelcoat provided wax has not been applied over them. I suggest first pressure washing the deck to get any residual metal off the deck then treating the rust stains with Ospho diluted 3 parts water to 1 part Ospho. Let it sit for an hour then rinse it off well with water. Just a fair warning on this, this treatment is an excellent fiberglass cleaner and unless your deck is super clean you will end up with white spots all over your dirty deck. Rust particles can often leave a thin rust colored haze on a deck that is not obvious until you clean the heavy spots. To clean this haze I put a quart of Ospho in a two gallon garden sprayer and fill it with water. I mist the deck with a light coat of the mixture and let it sit for an hour. I then rinse it with water, after which the deck is so white you have to have sunglasses on to look at it. Two Gallons is enough to do my whole cat, so a gallon should be enough to do your boat. The rust is converted to Iron phosphate which is water soluble so it rinses off, however it does nothing to the base iron, so if there is any residual metal that hasn't turned to rust the stains will reappear. That's why I pressure wash it first.

[Fishbone 1]

I know this may sound strange but if you go to the grocery store or Walmart, in the laundry section, look for a product called "Whink" it is a laundry rust remover that comes in a small (6 oz. ish )brown bottle.Works great, very fast. Apply , watch stain disappear, rinse then best to re-coat area with a wax coat or protectant. Whink is Oxilic acid based and only cost a few dollars. way cheaper than Off-On at the marine store $20 bucks a quart.

[crisadee]

Oxalic acid- I used it, works wonderful. Here in France, it costs about 1,50€ the can, it's a powder you have to solve whith some fresh water, for the price you get enough to treat your boat and all of the marina 20 years long!
Just brush gently whith a soft brush poured in the acid, and rince a lot whith fresh water, and that's it!

[BBViper]

I'm in the FSR camp. Amazing stuff. Had a bunch of rust stains in cockpit. Left FSR on them, forgot about it. came back the next day was amazed at how clean the cockpit was. not a trace.