Like nearly everyone else in the world, our near-term plans have been been put on hold because of Coronageddon. Since we’re stuck onboard at the dock instead of exploring South America by land, we’ve decided to make some lemonade out of our lemons – we’re using our downtime to tackle some lower priority boat projects.
Removing the hardware from the mast where there were some paint bubbles
One of those projects is cleaning up some light corrosion on Madrone’s mast. Over the last year or two, the beautiful paint job on the mast has started to show some light bubbling in a few spots. The culprit is poor original installation of some of the fittings on the mast.
Yuck! Bubbling paint and light corrosion under some mast hardware
Nearly anytime two dissimilar metals (like Madrone’s aluminum mast and the stainless steel hardware used to attach fittings) are connected in the presence of an electrolyte (like saltwater spray from sailing upwind), galvanic corrosion occurs. The same chemical process that creates voltage in alkaline batteries, the result of galvanic corrosion on the mast is the creation of small bubbles under the paint.
Our homemade cardboard painting box to prevent overspray from our spray paint primer
Left unchecked, this corrosion can penetrate deep into the walls of the mast and weaken the structure. In our case, though, we caught it early – the corrosion was only on the surface and wasn’t really a threat to the integrity of the mast.
The solution to this problem is to use some insulating paste on the threads and under the heads of stainless fasteners that penetrate the aluminum mast. However, applying the paste to each fastener in a thorough and neat way takes a fair amount of time, so this step is often skipped when the original installer is in a hurry. That’s what likely happened with our mast.
Mike in the painting box
The corrosion didn’t really start until we reached Mexico. At that point, the warm, salty water started to really accelerate the process, and the fact that the corrosion caused the mast paint to bubble made the situation look a lot worse than it actually was.
After sanding the bubbled paint and removing the corrosion we applied the primer
We sanded the paint off the corroded areas of the mast, thoroughly cleaned the areas with acetone, and prepared to paint. Since the only primer we have on board is in a spray can, we used some cardboard to make a small portable paint booth to prevent overspray. We’d spray a thin coat before removing the cardboard and retaping it around the next spot.
The topcoat paint we have onboard is not an exact fit to the original color or finish of the mast, but it’s surprisingly close for something that we just happened to have at hand. The only downsides are the requirement to sand between each coat and the fact that we needed 3-4 coats to get a good finish.
The final product. The paint color isn’t a 100% match but it’s fairly close.
After many days of sanding, prepping, and painting, the mast is looking good and no longer bubbling.
