Salt spray test verses real world performance for various types of corrosion protection?

[Deemer]

I have an application in which we need to connect an aluminium plate to a aluminium block using two bolts. There could be a fair amount of wind load at this joint so it must be fairly strong and it is also located in a coastal salt water area.

The plan was to use hot dipped galvanized hardware to help with corrosion, as they have long proven history. The down fall is that the added thickness of zinc coating requires oversized threads tapped in the aluminium block. This is problem as we do not have the correct oversized tap and would have to get one custom made.

I have looked at various other bolt coatings claiming high corrosion resistant, i.e. Geomet, Dacromet, Ultra Corrosion Resistant etc. All of these have displayed images of 1000 hour salt spray tests indicating they far out perform hot dipped galvanized. I would have taken this to be true except I came across another source that indicated salt spray tests weren't necessary true indications of real world performance.

It's hard to argue with the few hundred years history of hot dipped galvanized. So my question then, is a salt spray test a true indication of real world performance for corrosion protection?

 

[EdStainless]

You say that this is coastal, will it be exposed to the open so that it will be washed by rain?
If not then you need a lot better corrosion resistance.
I would suggest looking at sealants and coatings for the connections.
A build up of salts in the joint will lead to much worse conditions than in a salt spray test.

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Plymouth Tube

 

[mshimko]

Regarding: "I have looked at various other bolt coatings claiming high corrosion resistant, i.e. Geomet, Dacromet, Ultra Corrosion Resistant etc. All of these have displayed images of 1000 hour salt spray tests indicating they far out perform hot dipped galvanized. I would have taken this to be true except I came across another source that indicated salt spray tests weren't necessary true indications of real world performance. "

1,000 hours of exposure in a salt fog chamber translates to....1,000 hours in a salt fog chamber, and little more.