Brown Stains on Fiberglass

[st599]

We've been struggling with staining on fiberglass this year.

We can clean the hull with oxalic or grunt, the boat looks fine, apply polish and It looks better, but within 2 months it's back to being terrible.

Is there a product to deep clean the GRP? We're wondering if we're just bleaching the surface? Or is there a better polish to use, or is there something that needs to be done to seal the surface?

 

[GEM43]

We've been struggling with staining on fiberglass this year.

We can clean the hull with oxalic or grunt, the boat looks fine, apply polish and It looks better, but within 2 months it's back to being terrible.

Is there a product to deep clean the GRP? We're wondering if we're just bleaching the surface? Or is there a better polish to use, or is there something that needs to be done to seal the surface?

There was a thread about this recently where unsurprisingly there were various differing opinions. I always Oxalic acid and then wax. Multiple layers of 3M wax to be precise. All that I can say is that it works for us and sucessfully keeps the waterline from being cumulatively discoloured.

 

[KevinV]

We've been struggling with staining on fiberglass this year.

We can clean the hull with oxalic or grunt, the boat looks fine, apply polish and It looks better, but within 2 months it's back to being terrible.

Is there a product to deep clean the GRP? We're wondering if we're just bleaching the surface? Or is there a better polish to use, or is there something that needs to be done to seal the surface?

Time to rub it back perhaps? My deck is at that stage - impossible to keep it clean

 

[William_H]

I have aalways had this problem with white GRP above the water line. Oxalic or any other acid will clean it easily. (even lemon juice) Just give it a few minutes to work then wash off. I actually clean mine in water with me swimming around the boat with little spray bottle. Yes avoid the spray. I do not know of any treatment that will avert the stain. ol'will