Why does some chrome rust?

[f_inscreenname]

It doesn't matter what type of valve cover (chrome) I use they all seem to rust after one season. All the rest chrome on the boat doesn't have a spot of rust after many years. Is it the base metal? Cheep chrome? Is there any thing I can do to prevent this. Already tried clear coating with no luck.

[exodus8]

i dont know if this will help, but sacrificial anodes might, i dont really know the science behind it so u might want to look it up on the net, but basically u "sacrifice" a weaker metal thats easy to replace on the motor an all the rust attacks that weaker metal first, u should be able to look up more info on the internet

[Major Woods]

The chrome does not rust, it's the cheap base material under the chrome that migrates thru to the surface.Some chromes are plated on to thin and will stress crack on a micro level allowing salt/moisture to attack base material. When this happens it appears that the chrome itself is rusting.Expensive valve covers are tripple plated to withstand harsh enviroments.

[Bond-o]

Polished Aluminum.........