It's easy to think about corrosion if you're doing work on the seashore, or in a battery plant, or even in a plating shop. Yet, you often have such problems in the most mundane locations.

One, common around here, is our alkali soil. The common "Bell" box that we use outdoors is absolutely unsuited for direct contact with earth.

First, because - gasket notwithstanding - they invariable get filled with dirt and roots. Second, corrosion.

Here's a fairly recent install:



This was done, even though, just a few yards away, was this box:



There's simply nothing left of the box. True, the plant matter from the bush probably didn't help ....

I think the PVC boxes are better in any corrosion prone area.
We have the same thing on boat docks. A bell box won't last a year before it starts "chalking" away.

PVC, stainless steel, aluminium, and gavanized steel for my wet and corrosive environment (sea water). Bell boxes hold up pretty well up here.

For the most part, the wettness I deal with is rain and lots of it so for the most part, it is non-acidic. The sea water is a whole different animal. The salt likes to eat ferrous metals if left unprotected.

From my underwater equipment days, we would not mix aluminum plate and stainless steel hardware, where they would get wet. The aluminum would just corrode faster.

Larry

Aluminum and stainless together is always bad news in an electrolyte like salt water. There is a teflon based goo you can coat the junction with that makes it better but eventually the stainless will start eating the aluminum.

Interesting topic, John,
There is a galvanic chart around somewhere, I saw it some years back, it shows which metals will corrode when placed with other metals and to what degree, this is, I might add, first year apprentice electrical theory.

Having said that, I work in an environment (dairy sheds) where anything is either PVC, stainless steel or heavily galvanised steel pipe.
Anything that even remotely touches concrete, is always stainless.

I remember back when PVC enclosures became prolific in the trade here, some you bought would last quite well out in the weather, some just fell to bits, due to the sunlight, thankfully most of them problems have since been ironed out.