These gutters were apparently painted with an ammonia-containing latex that formed blisters which later ruptured and formed scabs (tubercules). I had to sand to bare metal and use JB Weld putty inside the gutters in some areas that were pitted completely through.
The BM technical representative recommended 2 coats of XIM Urethane Modified Acrylic (UMA) for spot priming bare metal areas. The gutters look so bad after cleaning that a full primer coat appears necessary to cover tiger striping from locked in tree sap stains and brush marks from the prior repainting. I scuffed up these areas with 100 grit paper to remove brush marks, but did not sand to bare metal.
Is it OK to use a DTM primer over the UMA spot primer, before applying topcoats of BM's MoorGlo acrylic latex? Would you tend to think 2 topcoats are necessary? I tinted both primers the same as the paint.
Last edited by Sand&Scrape; 04-18-2012 at 02:39 AM.
You would be far better off and trouble free to just replace the whole gutter not play wack a mole with leaks.
Your trying to deal with to many factors that will effect the bonding of anything you try to do to it now.
If you prime the bare aluminum and weld putty with UMA, there is no need for DTM primer. Over prepared, painted aluminum, just apply the finish. Yes, I would apply two coats of finish. Or, just apply a full prime coat of UMA, then apply the finish. I don't see a need for two different primers. Painted aluminum does not need a primer.