why did my cooktop screws sieze, when boiler screws don't

Plumb Bob

Homeowner here.

The screws in the burner bases of my cooktop turned black soon after installation, and after 4 years they seized. The heads stripped from attempting to unscrew them, and I had to pay through the nose to get them extracted so I could replace the spark rods. Repairman tells me this is a quite common problem, in ovens as well, it keeps them in business.

But this doesn't happen in my Munchkin boiler. The nut that's holding the back insulation plate, for example, is right next to the burner and must get quite hot, but it is pristine (no discoloration, no problem loosening or retightening it). There are other screws (e.g. in the boiler front cover) that must also get very hot but are in good condition.

What's the difference? Do boilers use a special alloy, or is it something else? I know you can't use stainless because it seizes easily.

Just trying to figure out if there is a way I could avoid having the same cooktop problem in future.