In my machine theory and design class the other day i found out something pretty interesting.
Chrome increases metal failure by 50%!!!!!
My teacher was saying this as everyone had started to leave the class and i was like.... wait.... WHY!!!!!!!
And basically it'* because of the internal stresses it puts on the metal.
Maybe alot of people know this and they didn't tell me????
I thought it was pretty interesting.
How many people already knew?????

Chrome is hard. Hard is brittle.

I ment chrome plating.

Maybe he'* referring to trapping moisture underneath? If it'* a good uniform plating on properly prepped base metal, it'll last for years. Until you get your first fender-bender and expose it to air. Rust on steel is oxidization. It needs air to do it. No air, no rust. Think of the plating as the 'air shield' for the metal underneath. Let air in, and a little moisture in a protected environment, and it can rust undetected for years.

For work applications if I need a plating, I generally go with nickel. It'* softer, and more likely to be misshapen rather than crack. Nickel isn't nearly as brittle. A uniform nickel plate on an aluminum part gives it alot more surface strength and abrasion resistance than anodizing.

I guess chrome would be better than aluminizing for the durability. And i see what your saying about the air getting under the chrome and trapping it causeing rust.
I think that what my teacher is trying to say though is that since the chrome plating is hard, like you were saying, the metal will have a hard time expanding and contracting because of the chrome on the surface. Maybe it'* because of the carbon content of the chrome? Does chrome contain more your average 10xx steel?

^^not just expanding and contrating though, i mean the chrome obiusly will have a diffrent yeild point when reacting to stresses