The process of electrolysis is quite interesting. One metal becomes eaten away/disolved - the anode. Which metal dissolves depends on which end of the anodic/galvanic scale it is at. Graphite, platinum and gold are at the bottom - least galvanic/anodic, so have the lowest potential to dissolve, whereas magnesium, zinc and mild steel are the most galvanic and most likely to dissolve. Copper is somewhere just below centre. Nickel and silver are very low, not much above gold.

According to the galvanic table, low carbon steel is more galvanic than brass, so presumably the area around the pivot pin would act as the anode and be dissolved, which probably explains why we do not see many corroded away brass pins. However, for the process to proceed an electrolyte must be present - water with dissoved oxygen in it, in our case. As the razor only gets wet for a short time, the process is probably negligable anyway.

The practice of copper-sheathing the bottom of wooden ships, BTW, had nothing to do with killing or preserving things - it just made it impossible for the wood-boring bivalve the "teredo shipworm" to bore into the wooden planks - they could sink ships! It did have a little to do with electrolysis though - they used to nail the copper to the planks with steel nails and the presence of seawater+oxygen as an electrolyte made the nails act as sacrificial anodes and dissolve away - so all the copper fell off! Copper nails were the answer.

Regards,
Neil