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How to remove Fiberglass boat oxidation



Q. I have a 5 year old fiberglass boat with a green hull. I have heavy oxidation. I've tried heavy duty commercial compound and applied same with a commercial wheel. I was not able to remove the oxidation. Some people suggest wet sanding with a 600 grit wet sandpaper [affil. link to info/product at Rockler]. What do you suggest.

Thank you,

Lou DeMartino
- Smithfield, Virginia


A. Lou,
you say you have heavy oxidation but you sure don't say if it's above or below the water surface, do you?

My first suggestion would be to contact the boat manufacturer. If that doesn't work out, contact any FRP boat mfg.

Fibreglass doesn't like abrasion. If properly made, the outside would have a gel coat. This would be a thin coloured coating and would protect any fibres and SHOULD GIVE u.v. protection... if the right 'mix' were used.

Personally I've never heard the word 'oxidation' applied to fibreglass unless due to severe, mainly oxidizing acid attack. And your using a buffing compound to 'grind down' this problem will only make things worse.

Boat resins use just standard aliphatic polyesters, you don't need better (sic. acid resistant) ones. Try also the local supplier of fibreglass type resins. They could/should be able to help you ... and for advice on how to properly apply any coatings, a local frp fabricator will gladly give you some good advice, if you beg properly!

freeman newton portrait
Freeman Newton [dec]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



A. I also have a sailboat of approximately the same vintage as yours. It too, is dark green. The "oxidation" you are referring to is known as "chalking". If you live in a sunny area (such as Florida), a dark hull will chalk faster than in Northern waters where the boats may be under cover during the winter months. Dark hulls are beautiful when new, but are hard to keep looking good. The hull on our boat has the worst chalking on the starboard side. It is the southern side as the boat sits in the slip at the marina. I have tried my best to wax the heck out of the hull. Most marine waxes have UV inhibitors and that helps. However, since we bought the boat used...and the previous owner never worried about wax, we cannot bring back the deep color shine (no frosty whitish areas) that has already been lost. We were told by the manufacturer of the boat and several boat yards, that our only real solution was to paint the boat. Sigh. Paint has its own drawbacks, but I have seen beautiful, deep-blue Hinkley sailboats on the water. They have been painted with Awlgrip [affil. link to info/product on Amazon] type paint. Hinkley is a very reputable boat builder (and way too expensive for us to own!)who will not sell a dark gelcoat hull for exactly this reason. Someday, we will probably have our boat painted. Don't sand through your gelcoat trying to find that beautiful deep-colored shine....

There are "gel-coat restorer" products on the market. Read "Practical Sailor" magazine [at www.practical-sailor.com] before trying any of these. Practical Sailor is the Consumer Reports [affil. link to Amazon] of the sailing world. If you are a boat owner... I would recommend you subscribe. It has saved me a lot of time (and money) trying products that really wouldn't do what I wanted. (PS...I have NO affiliation with the publication. This is just my personal opinion).

Good luck... and Safe Passages,

Ronna Erickson
- Amherst, Massachusetts


According to the messages, the chalking can be easily removed by chemical way. Phosphoric acid will be a solution. Please try. There is a product in US and in China made of Phosphoric acid for rust cleaning can remove the oxidation. Please try.

There is a small skill if you can not get this product easily, just buy 250 cc 75 or 85% phosphoric acid, mixed with 1.5 liter of water. Use it to brush on the chalking area. Hold for few minutes, clean with water. Most of the chalking will be removed. Use rag clean the rest. Please let me know the result.

Steve Milano Leong
Marine product importer - Macau, China

Fiberglass Oxidation Remover

Affiliate Link
(your purchases make finishing.com possible)

Meguilar's Fiberglass Restoration

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(your purchases make finishing.com possible)


Q. I am trying to restore the main entry doors to my Church. The doors face north. They are heavy duty solid core wood doors that have a wood grained fiberglass surface. The color of the doors is dark brown to dull black. The color has faded on the outside of the doors so it appears there is efflorescence on the doors. Is there a product that is good for restoring the original color? Does this need to be stained and/or coated with a lacquer or varnish? The doors are subject to cold weather, snow but not a lot of sun.

Charlie Radich
architect - Cheyenne, Wyoming

August 5, 2009

Q. I have a bass boat that has a real rough feel to all of the horizontal surfaces. The hull and vertical ones are fine and slick. I'm sure it's from years of being out in the sun as I'm going to have to replace the seats due to serious cracking and rot. D

Does anyone have any suggestions? Thanks Rob

Rob Teem
- Cumming, Georgia

December 29, 2009

Q. Any please help. I have a high end 2001 fiberglass boat that is starting to show a dulling or fog type film at the waterline of the hull. I have try everything to remove this dulling with no success. (Is this oxidation ?). If so, anyone know of a "for sure" removal product that I can purchase? Yours truly very sad fiberglass boat owner.

David Gamble
Boater & Sportsman - New Iberia , Louisiana

April 11, 2014

It doesn't look like anyone has responded to you in the five years since you asked this question, so by now, you probably don't have the boat anymore.

If you do have the boat still, you're problem is 5 years worse.

If you're there still.... do you still have the boat and am I right that it's worse by now?
If your answer is yes, can you upload a picture?

Arlene Crowell
- Richmond, New Hampshire USA

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