Bow - metal parts
What metals have been used for the screw that tightens and loosens the bow hair? Is there any chance of rusting or corrosion?
Depends on the price of the bow.
The screw is steel, and yes, they rust. Don't ever use soap to lube it! Wax.
The actual tightening screw might be iron or steel but brass could be used. To lighten the frog region of the bow ARCUS has also made titanium screws. I know this because when I wanted a little more (relative) tip weight Bernd Müsing of ARCUS sent me a replacement titanium screw.
The screw shaft is steel, and the bit-it-goes-into is often brass and wears out.
Different materials are possible for the screw, from a basic steel to 12L14, stainless, and titanium. Steel can rust. Stainless and titanium will hold up better. However, what ever is used to lubricate the screw as well as dirt from the hands, works it way under the frog and can things.