My wife got her doctorate in Engineering Physics in England looking for an alternative conversion coating (that is the correct term apparently) for aluminum. She got down to looking at the atomic level in an electron microscope of how chromates and other compounds work. Chromate coatings do have health and environmental issues but nothing she or anyone else found works as well.
Bruce Clark and June Wan (PhD, aluminum coatings and corrosion in general)
Nonsuch 30, “Nonsuch”
Lake Ontario near Toronto
Bruce - You are a lucky man to have expertise like this in your household. Thanks for passing on the info about chromate coatings.
Today I removed both hanger pad-eyes and their opposing pad-eyes. The corrosion is worse than I thought it would be. Makes me want to re-examine all the stainless fittings that touch aluminum on both wishbone & mast to verify they are properly isolated.
For folks doing visual inspection without removing the pad-eye… ( HERE ) is what I saw. Then after removing the pad-eye ( HERE ) is what I saw. Much more extensive corrosion than I expected.
Looking at the underside of the Pad-eyes, ( HERE ) it looks like they were all coated with something that probably degraded over the years.
I enjoy tinkering, but it’s looking I’ll be doing more this winter than I planned. Stocking up on zinc chromate primer and wishing I did this inspection last winter.
Interesting. On the old Nonsuches they did not use pad eyes for the wishbone. Instead they welded in a plate of aluminum that went through slots on both sides of the wishbones. I guess slower and more costly to do than attaching pad eyes but you avoid the dissimilar metals problem. In my distant past (which is pretty distant) we would make a ‘gasket’ out of the plastic that milk jugs were made of. I think any thin, flexible, hard plastic, say 1/16” thick would do the trick. Combine this with Tefgel or similar on the threads of the bolts and you have isolated the two metals.
Bruce Clark
Nonsuch 30, ’Nonsuch’
Whitby YC, Ontario