How well does anodizing aluminum prevent galvanic corrosion when the aluminum is contacting 303 SS?

[fwe6455]

We have a situation where we need to take some weight out of a component. We want to switch the material to 2024 AL, but the component threads into another component made of 303 SS. The 303 SS component sees a crimp operation, so we are hesitant to change both to 2024 AL since we have dealt with aluminum cracking during the crimp process in the past. We will have the aluminum component anodized, but do we still have to worry about galvanic corrosion? The assembly will be used in fuel, so exposure to water moisture will be minimal.

 

[TugboatEng]

Without exposure to moisture or other conductive fluids, galvanic corrosion does not occur.

In my experience, lots of salt spray, anodizing will typically not protect against galvanic corrosion. I have seen one exception with a hard anodized plate.

 

[EdStainless]

What is the external exposure?
Is this in a plant? On a truck? Where?
In general no, anodize isn't enough, but if you can get away with using 303 (very poor corrosion resistance) then maybe it will work.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

2024 aluminum is also a poor choice for corrosion resistance as it is a copper bearing alloy.

 

[fwe6455]

I misspoke, the material would be 7075, not 2024.

The component would be submerged in fuel.

We could use 316 SS rather than the 303 SS. So the contact would be between 316 SS and 7075 AL anodized.

 

The answer is...it all depends.

Personally I do not trust thin coatings of any kind for long term protection. Your parts are in mechanical contact, so I expect a break somewhere, probably during assembly.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[TugboatEng]

The anodizing needs only to protect the components until they can be assembled and placed in service. Once submerged in fuel, the fuel will protect the assembly.