On Thursday, November 9, 2017 at 3:19:46 PM UTC-8, Joerg wrote:
Missing a couple of screws for mounting adapters and calipers. The frame
of the bike is aluminum.

Do these have to be from some sort of space-age special material? The
ones that came with the adapters (unfortunately only one pair each) are
magnetic, so it's steel.

Most of my M6 screws are Cadmium plated steel like they are used on
aircraft. Will that do?

I guess brass isn't sturdy enough. Anything else is locally unobtanium
in metric size.

For my flat mount brackets, I used standard SS cap screws purchased at the local hardware store. Those happen to be 5M, IIRC. The 6M caliper mounting hardware came with the brakes, and it looks like plated steel. No special alloys required. I don't think galvanic corrosion is a big deal with brake mounting hardware unless your roads are salted and you ride in snow.

-- Jay Beattie.