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Aluminum galling


I have CNC'd two pieces of aluminum to make a portable espresso machine.
The bottom is 2.3" diameter. The top is 3" diameter.
The top and bottom pieces gall so bad that they will not open. What can I do?
I tried FDA approved anti seize, but it looks gross, and I don't think consumers will want to see it while they make espresso.
If I was going to use a different metal for the lid, what should I use?
Water is pressurized to 160 PSI and heated to 212 °F deg.
Please help
What kind of aluminum should I buy?

Soren Brockdorf
- Jacksonville, Florida, USA

Hard or even conventional anodizing both parts may help or even totally eliminate your problem. Electroless nickel plating may also be a solution though probably more expensive.

Guillermo Marrufo
Monterrey, NL, Mexico


Does the top thread onto the bottom (cylinder, maybe)?
The problem could be tapered (pipe) threads --shouldn't use where frequent disassembly is necessary. Use machine threads (straight), anodized, and seal with a suitable o-ring.
If problems with a non-threaded assembly, anodizing may prevent the galling.
Note there will be a build-up per surface of about 1/2 the anodize thickness.
What aluminum alloy are you now using?

If hard water scale can occur, using stainless steel will allow cleaning with the common acidic scale removers.

Ken Vlach [deceased]
- Goleta, California

contributor of the year honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at, continue to benefit from.

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