Sanding, Chemicals or Compounds for Gelcoat

[Reverie]

Respecting the advice of Michael Stoops in my previous post of Gelcoat Restoration not lasting, I’m attempting to avoid wet sanding of the gelcoat. However, we’re stuck again. After repeated power application of another new section with M91 & M67 deep stains are not being removed. The gelcoat is significantly improved by the compounding, but not as good as it can or should be.

On a test patch, following M91 & M67, for those stubborn stains, I have wet sanded with 1,000 thru to 2,000 grit. The stain was removed - with relative ease. Another M67 following the sanding and it looks fantastic.

The actual composition of the stain is uncertain – It ranges from yellow, to brown, to black – generally originating from rain running off the deck which was filthy including industrial atmospheric pollutants, general road type dirt in the atmosphere, and rust type stains from stainless steel fitting.

If 91 & 67 is not working, and wet sanding does work but is not recommended, would the use of chemicals be a better alternative to wet sanding?

My local paint shop has just started carrying a product by CRC called MaryKate. The product contains, Hydrocloric Acid, Phosphoric acid, Ethoxylated nonylphenol and Oxalic acid – One nasty mix ! I have not applied this to the hull hence have no idea is it will work – assuming it will – as they say it will – Is this (or any other chemical) a less destructive method than wet sanding an aged gelcoat which is desperately attempting to shine ?

[Reverie]

Re: Sanding, Chemicals or Compounds for Gelcoat

We're still hoping for someone with technical knowledge to reply, however, while waiting we have tested CRC -MaryKate Hull Cleaner - It works just as good as the promotional material says it will - apply with a brush and rinse it off with a hose. Magic - stains are gone ! For deep embedded stain within the aged gelcoat - multiple applications were required, and I did use a bit of a 'scrubbing' action - with nothing more than the throw away brush used for the application of the chemical. Effort measured in minutes - could not be easier. The end result appears to be 99% as good as wet sanding. Unfortunately, we're still none the wiser if this is a short term cosmetic fix which is actually doing more harm to the gelcoat. CRC claims it will not harm gelcoat or fibreglass - But then I did not think wet sanding would do any more damage than minute removal of the surface until Michael Stoops enlightened me. The question remains: Which bad boy does more damage to aged gelcoat - wet sanding or chemicals ?

[Detailing by M]

Re: Sanding, Chemicals or Compounds for Gelcoat

your asking auto detailers about refurbishing rv's.
why not check rv sites. I'm sure someone on those forums will have your answer.
and you can always check autogeek there are thousands of experts there on every single subject.

[Reverie]

Re: Sanding, Chemicals or Compounds for Gelcoat

It's a boat - not an RV - The chemicals would melt an RV before you could reach for the hose.
Promise .... I've searched and have found no other source of real knowledge than found on this site.
I've got an arsenal of Meguire product already accumulated - ready to follow behind that first attack on the embedded stains which Meguire is not reaching .....
I do appreciate this is predominately auto detailers and accept that the question is outside the bounds of most auto folks - but then I've learned heaps by the Meguire's rep advising I'm making matters worse by sanding ..... so I'm hoping, that someone reading the marine forum will have the depth of technical knowledge to save the day. Once we save the boat I hope you can help with the car too :-)

[Detailing by M]

Re: Sanding, Chemicals or Compounds for Gelcoat

well here's a chance for you to try stuff and figure it out?
but post on autogeek, a lot more people there

[oneway]

My friend, is this the same boat that was not tended to for twenty years? If so, the harsh reality may be that the gel coat is simply just breaking down. These surfaces do reach the point with severe neglect that your just not going to be able to bring it back to 100%. My guess because I haven't seen it obviously is to cut the surface, which you've already done, polish it back out than simply seal it. The waters are harsh so a traditional wax is not good enough. Use a product that is designated for what your issues are. Than maintain at that point. When I work on oxidized gel coat, I love this combination, 3M super heavy duty compound, its really gritty on a wool heavy duty cutting pad or meguiars maroon cutting foam pad on a rotary. A DA can work but you need the power to cut. Im sure you know all of this already. Just putting my two cents in my friend. Be blessed...

[Reverie]

Re: Sanding, Chemicals or Compounds for Gelcoat

Thanks Oneway - and sorry for the delay - did not receive email notification of your reply and had not checked before tonight. Yes, it is the same neglected boat .... but she is receiving vast amount of attention now and she will survive. The following works:

CRC MaryKate hull cleaner - a nasty combination of chemicals (see original post for specifics) that will blow your mind - wipe it on gelcoat - rinse it off - don't let it contact anything else - the gelcoat stains will instantly disappear. The product is cheap as chips, and microscopic quantities are necessary to achieve brilliant results. We follow with M67, M45 and M63 the results = new boat appearance of the gelcoat. Because of the age and porosity of the gelcoat, plus the filthy air at the boat yard, we are quickly re contaminated with rust type partials. A very quick and easy wipe down with CRC MaryKate - only on the stained/re-contaminated parts, followed by a quick application of D156 and we're back to new boat gloss.

Still hope someone with technical knowledge will advise if there are any adverse effects of the CRC chemical bath - of course CRC claims no ..... I'm now also not clear on what you are suggesting by "simply seal it" .... seal it with what ?? Yes, I have worked with 3M super & wool and they do work - but I prefer Meguiar's ..... I think we have the cutting side sorted ... it's that sealing bit which you might be eluding to that is definitely not sorted, so if you could clarify it would be much appreciated.