Does happen on cars. Just look at aluminum components in a 60's - 70's era car that hasn't had the coolant maintained well. The most reactive metal goes first, generally "sacrificing" itself before the adjacent less reactive metals corrode. Apply a small amount of electrical potential and the process increases rapidly. Add in a substance that enhances the flow of electrons ... like an acid and it increases even more, add heat and again the process accelerates.
Also known as galvanic corrosion, or bi-metallic corrosion. A battery basically uses the same process in reverse to create voltage. Metals like iron, aluminum, magnesium, zinc are very reactive, while metals like gold, silver, bronze, nickel, SS (due to the nickel content) are less reactive.
Several years ago I used some bare 6061 1/4" thick aluminum angle to reinforce the goose neck hitch on my truck. They were mounted underneath the bed with the through bolts to the hitch going through the bed and into the hitch. They were the only pieces of aluminum within several feet of where they were mounted, and they probably received a bit of voltage with the trailer probably trying to ground out through the hitch when pulling a lot of current from the truck (trailer had living quarters) rather than grounding just through the trailer connector.
Within three years, living up north, those aluminum pieces turned to dust. Never saw anything like it, was the perfect storm of dissimilar metal corrosion. These were substantial pieces of metal, four of them, you could break them in half with your hands. Luckily I caught them before race season that year and replaced with stainless steel.
As a side note ... that truck had an incredibly small amount of rust on it for it's age and mileage in a northern climate .... makes me wonder if those aluminum pieces saved it from several years of corrosion by sacrificing themselves. Back in the day you used to see sacrificial zinc anodes for sale for cars, just like seen on ocean going ships.
|