Isolated "pimples" on epoxy gelcoat??

[Longshanks]

Isolated \"pimples\" on epoxy gelcoat??

Just in the process of scraping off the old antifouling and inspecting the hull. It's in truly remarkable condition for for an old boat and the epoxy gel coat looks as good as new some 15+ years after osmosis treatment. However, I came across a very few (3-4 so far) isolated "pimples". They don't have the dome shaped appearance of osmosis blisters, but are hard, almost pointed irregular shaped lumps about 5mm across with a soft white powdery material inside that goes 2-3mm deep into the layup. A small pimple with a head is the best description. Easily fixable, but I wondered if anyone knows what these might be? Could they just be blemishes in the original coating, or some kind of local wicking? In at least one case the white material inside seemed slightly wet.

 

[oldsaltoz]

Re: Isolated \"pimples\" on epoxy gelcoat??

G'day Longshanks,

A little difficult without a picture or two but here goes.

It sounds like some of the original gelcoat may not have been fully mixed leaving some small dry pockets, the resin in the surrounding gel coat may have been pressed in if the inside was given a light roll to flatten a local high spot, left because of the dryish gel coat mix underneath.

The end result would be a thin layer over a very small but dry area. As time passes the material may have had some contamination that has caused the original dry material to swell and cause the small defect you now see.

We still very little about what will happen inside epoxy resins over long periods being exposed to anything you care to take a guess at. it may even be the result of contamination in the first place.

See if you can post us a picture of the open one and one that is still closed.

I hope this helps.

Avagoodweekend......

 

[wotayottie]

Re: Isolated \"pimples\" on epoxy gelcoat??

I had a boat teated for osmosis and which exhibited the same symptoms after a couple of years. Turned out to ba a failure of the epoxy due to cold temperatures in treatment and formation of amine blush. Blisters formed which in my case contained an alkaline liquid. That was the sign that it was an epoxy problem rather than the acid liquid in osmosis blisters.

Get yourself some litmus paper and check out the holes.