Stainless steel can be both magnetic and non-magnetic. However, if the nail is not magnetic, it's most likely stainless steel.
You can often tell by looking at the screw:
Gray coating = hot-galvanized
Glossy metal = electroplated/chrome
Normal glossy = stainless steel or new regular steel
Darker coating and slightly rusty tendency = steel.
Otherwise, it's about damaging the surface and putting it in a humid environment.
You can often tell by looking at the screw:
Gray coating = hot-galvanized
Glossy metal = electroplated/chrome
Normal glossy = stainless steel or new regular steel
Darker coating and slightly rusty tendency = steel.
Otherwise, it's about damaging the surface and putting it in a humid environment.
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Unfortunately, "rostfritt" is not an unambiguous term. For screws, the classes A2 and A4 are used. It is only A4, = syrafast, that is rustproof in all environments. I think you need to subject the screw to a tough treatment to find out its status. Place it in a jar with salt water.