With the plywood porthole surrounds finished, next I had to deal with the primer around the aluminum lip of the aft window openings. When I removed the plywood, it became clear that there was bedding compound around each of the window openings that was now coated with primer. When the plywood came off, it took some of the bedding compound and primer with it, revealing some places where the primer wasn’t properly adhered to the aluminum.
That little chip came off with the bedding compound. Obviously, we didn’t do the prep work right in these areas when we first primed the boat in 2009. Better to catch it now than to have the paint fail in a few years.
The tar-like bedding compound was hard stuff but peeled off of the aluminum with a scraper without too much work.
This sealant was different than the tar-like stuff and came off very easily. The primer had adhered to the sealant very well, but underneath the sealant there was white powder on the aluminum lip. The paint at this joint would have probably failed pretty quickly.
I put a razor blade to the crack and the chip above popped off. There was a dusting of aluminum oxide under the primer here. I’m guessing it got wet when the boat lay fallow after the paperwork SNAFU, and corrosion started to grow unseen.
The little crack that turned into a chip actually had primer failing around it for several inches. I found several of these while cleaning up the ten window openings. While I was working the grinder to get back to clean metal, I touched all of the edges of the aluminum window openings all the way around and also on the interior surfaces back to where the original primer and bitumastic coating were in good condition.
Per the Max Cor instructions, alumaprep and alodine treatment is not required in these areas when the aluminum is freshly prepped.
It took me a whole day to remove the bedding compounds, fix the chips and apply primer, but it was well worth the effort. Now there is a monolithic layer of well adhered modern epoxy primer from the exterior of the boat over every surface where I’ll be bedding the portholes. Hopefully, this effort will pay off with many years of service from the shiny hull paint that’s going to be sprayed soon.