Today has been long and hard work. However, we have managed to sand/grind, wash, clean with acetone and then paint with Epoxy Primer both our masts.
Part of the challenge is that for the primer to stick to aluminium you have to paint very quickly after sanding. At least within 8 hours/the same day. With the amount of sanding preparation our main mast (in particular) needed this was a big ask.
It took a while to find the best technique. It isn’t always obvious how deep a scratch/corrosion pit goes. So I found it best to just tackle the worst with the grinder (using a ScotchBrite pad to avoid metal contamination). Then I sanded using the orbital sander (by keeping one battery on charge while using the other I was able to work continuously). I used 120 grit with with occasional 80 and 240. For any marks that didn’t disappear reasonably quickly I switched back to the grinder.
For some reason the starboard side of the mainsail track was much worse than the port side with lots of deep scratches. There were also lots of marks from shackles that must have been allowed to bang the past in several concentrated areas.
Jane hand sanded all the tricky areas like the masthead, tracks etc.
After sanding we washed the debris off with water and a sponge. Fortunately it was still very hot an sunny at that point (about 4:30pm) so it dried off really quickly.
Then a quick clean with Acetone, judging by the cloths we used for that it was well worth doing.
Next came the painting. International Paints give you a 10 minute rest once the paint is all stirred, mixed and then stirred again), this was very welcome 🙂
Fortunately, even by the time we were finishing painting at about 7:00pm it was still warm enough for the first parts to be touch dry, so we were able to rotate the masts and paint the parts that they had been resting on.
Here are a few photos of the progress through the day.
For most of the day we didn’t really think we would get this far. But once you start you are pretty much committed or lots of the sanding will be wasted if the Aluminium is left long enough to oxidise. We had a very late lunch as Jane had to make an emergency run to Toolstation for more sandpaper, by then it didn’t feel like we had more than about 1/2 the main mast sanded.
Anyway, this feels like a huge milestone completed. There were a number of places where we felt that we had caught corrosion just in time, much longer and we would have had corrosion holes in the masts and a much bigger task.
Tomorrow, epoxy filling and then 2nd coat of primer (hopefully).
Well done! Great progress
Hi, great write-up on the timing challenges involved. You mentioned you used International paints, I’m guessing this is Interprotect epoxy primer. The TDS for interprotect suggest that their Etch Primer should be applied before Interprotect in their surface preparation notes for Aluminium. Of course, this is yet another product, and time, etc. etc. I have a support question with AkzoNobel on this, not yet responded. Did you consider the etch primer? I read conflicting reports on whether etch primer is a good idea in highly corrosive environments, like yacht spars.