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I am no expert on screws. When I go buy some, I'm typically handed screws that have a silvery color. I have never asked about the metal composition. Still, occasionally I notice you can also get sets of black/dark-gray colored screws, like these:

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and that they're intended for use with drywall.

I'm assuming the color is not just a coat, and that they're indeed made from some other amalgam/material than your typical silvery screws. Are they also (significantly) weaker, for a given diameter? e.g. do their heads break off more easily? Does cam-out remove more of their material than regular screws?

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    in my experience, black screws are much harder than shiny ones. Failure modes are different, so it's hard to judge "weakness" w/o being more specific. They don't bend or give, they snap. But they are quite strong and won't snap/break until more force is applied to them than would bend a "regular" fastener. A cam out would round it out less and whittle your bit more.
    – dandavis
    Jan 2, 2022 at 22:00

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They are steel, like most other screws. They are typically heat treated differently than a standard wood screw, and they are also shaped differently, and thus tend to be more brittle. As such, "structural screws" are recommended over drywall screws for building structures, rather than holding drywall to things.

The coating is just a coating/surface treatment (phosphate, IIRC) that's supposed to prevent them making enough rust to be objectionable before the drywall compound (near-universally referred to as mud) dries - they will certainly rust given more time+water, though.

The head shape is not a standard countersink - it's designed to pull down the paper on the drywall without breaking it (when screwed in far enough but not too far.)

Plenty of them have been used for "improper uses" but there are better choices for the other uses.

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