We have noticed on some earthed equipment that the pan head machine screws that connect the earthing wires to the metal case are black in colour.( shake proof washers are also used)
Looks like some of these black finishes are conductive ( like black nickel / Zinc-Iron / black chromate ) and some are not conductive (like a oxide finish )
I would welcome any help or advice on whether black finish machine screws should be used ? ( especially the non conductive oxide ones)Although I understand the black finish on these screws is so so thin and maybe wears off when screwed together ,
Looks like some of these black finishes are conductive ( like black nickel / Zinc-Iron / black chromate ) and some are not conductive (like a oxide finish )
I would welcome any help or advice on whether black finish machine screws should be used ? ( especially the non conductive oxide ones)Although I understand the black finish on these screws is so so thin and maybe wears off when screwed together ,