we mount a tin plated copper ground bus bar in our electrical enclosures for customer connections. The bus bar is tin plated but process requires tin plating to be performed before holes are punched. But what if the bus bar is plated after holes are punched in? Obviously tin is not as conductive as copper (almost 10 times the resistivity); will that make the ground bus not usable? We have received a batch of these and this is the case.