white stuff in sump-help

[travismcgee]

had a couple of large sumps made to fit in garage out of 3/4" plywood and fiberglassed on the inside. they were glassed several times (to stop leaks). they are currently full of fresh tap water, but when wet a lot of white "stuff" appears-some comes off with scrubbing,most doesn't-the person who made these said it will not leach or harm anything once i get things in the sysytem and he has owned a saltwater shop for years-any ideas on what this might be? thanks

 

[KevinM]

Does it come off if you scrape lightly with a sharp blade?
Some resins leave a waxy residue on the surface after curing, and I don't know how it would react with water. It could exhibit the whitening you're seeing, I suppose, and possibly bond somewhat with the surface.
My background with epoxies is in R/C planes, where it's always sanded. I know the resin itself is inert after a good cure, and I would imagine the waxy stuff is too, but I wouldn't bet the tank on it. Check the website of the manufacturer of the resin for some specs, and maybe they have a FAQ, as well.

K

 

[travismcgee]

thanks for the reply--the white only shows up when wet, when dry all looks normal..i have only applied some serious elbow grease with a rag and can then get a bit sometimes.most doesn't come off or show signs any will come off..when sumps are drained it immediately goes back to clear.he mentioned he cut the resin with acetone once.greatly appreciate any help