dissimilar metal connections

[broekie]

I know that connecting dissimilar metals is not recommended. I've looked at galvanic corrosion charts, but I've had a hard time making good sense out of some of the tables I've seen. My specific question is about these connections:

1. stainless steel to galvanized steel

2. aluminum to galvanized steel

I have a mechanic equipment cabinet that I need to strap to a galvanized steel pole. What is the best material to use for the straps - aluminum or stainless steel? One client has used stainless steel straps for years with no problem, but a different client is prohibiting that connection. We're going to go with what the client wants to do, but I'm curious for my own knowledge which is better. This is an outdoor, non-corrosive environment. Thanks.

 

[KENAT]

While it doesn't change the fundamentals, what kind of environment is your equipment going to be in?

Also, when you say aluminum or stainless steel are you talking bare material or what coating etc?

At a previous aerospace/defense company we typically avoided using SST to aluminum in lieu of zinc plated steel to aluminum. (The aluminum was normally anodized).

At my current place we use SST fasteners into aluminum (sometimes bare, sometimes chem film, sometimes anodized but that probably doesn't' get in the threaded holes very well) all the time with no problems. However our kit is generally in fairly benign lab environments.

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[broekie]

Bare material. No coatings. Outdoor environment, but not corrosive.

 

[KENAT]

If you don't get the answer you need here in a day or two, check forum338.

Posting guidelines faq731-376

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(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Ron]

I use SST fasteners in aluminum routinely. General environmental exposure, nothing exotic.

I do not recommend galvanized fasteners for aluminum for a simple reason..I've seen them corrode faster. When aluminum and steel are connected, the nobility charts say that aluminum will corrode first. That's true, but note that the first general corrosion of aluminum creates aluminum oxide, which passivates the surface. When that happens, the corrosion potential reverses and the steel corrodes like hell.

 

[EdStainless]

I have tended to use Al with galv, and not SS. The Al and Zn are similar so there is little galvanic corrosion effect.

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