I decided to try an anti seize compound on a couple MP aluminum molds, specifically on the sprue plate pivot bolt and the two handle bolts. This was the Permatex version in a tube, containing aluminum, copper and graphite. It’s rated to 1600°. I put just a thin layer on the bearing surfaces, specifically avoiding the threads.
BIG mistake.
After a single casting session, all the bolts seized up, jamming after maybe a quarter turn. I could only get the sprue plate bolt out, and found part of the threads full of hardened silver material (the same color as the anti seize) that is very difficult to remove.
The molds had been taken apart and reassembled a few times before without problem, and I’m sure I didn’t cross thread them.
I tried putting a dab of the Permatex on the mold preheater: a piece of steel on a coil hot plate whose surface gets to ~500°. It sizzled as it liquefied and ran before smoking and drying into a crumbly cakey silver powder. I’m guessing the compound migrated into the threads and decomposed from the heat in the blocks, though it never got near the upper limit of the operating range.
The molds still cast fine. It’s just that now the handles are permanently mounted, and I’m not sure how long the threads in the sprue plate bolt holes will stand future use.
Anybody want a barely used tube of Permatex anti seize?