[Sand&Scrape]

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.

 

[joecaption]

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.

 

[jsheridan]

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.