Galvanic Action between SS and Ti

[butelt]

I need some information on the galvanic action potential between stainless and titanium. If I have passivated 316 stainless and 6Al4VTi in direct contact in a humid (and potentially salty) environment, what risk do I have of corrosion?

Some sources I have read put SS and Ti on almost opposite ends of the galvanic table, but others have put them closer together. I understand that in order for galvanic corrosion to occur an electrolyte needs to exist. Can salty humid air act as the electrolyte, or does it need to condense before there is any risk of corrosion.

Thanks for the help!

 

[stanweld]

While working on the Space Shuttle attitude control rocket valves, the original design called for sandwiching a 316 SS part between 6/4 Ti and a more noble nickel base alloy. The 316 part looked like swiss cheese (crevice corrosion) after salt fog testing. It was replaced with a Ti alloy part and the valve passed the NASA mandated salt fog test.

 

[EdStainless]

The issue isn't galvanic corrosion, the potential difference isn't that much. It is simply that 316 has poor crevice corrosion resistance.
If you used a super-austenitic or super-duplex SS it would hold up fine.

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Plymouth Tube

 

[butelt]

Thanks for the advice.

What about anodized aluminum to titanium? Is galvanic corrosion then the main issue?

 

[rmw]

Some simple googling will produce several sites that show the galvanic series and give the information you are asking. Seeing the tables and where the relative poistions of various metals will help you get a grasp of what you are asking and maybe help you make a good choice for a metal paring for you.

Here is a start.

http://www.corrosionsource.com/handbook/galv_series.htm

rmw

 

[EdStainless]

With Al you have to believe that the anodize is porous enough to not block corrosion. Coupling Al and Ti will lead to rapid attack of the Al.

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Plymouth Tube

 

[strider6]

galvanic corrosion is a function of different factors and the relative position in the galvanic chart is just one.. you've to consider also the area ratio, electrolyte, temperature..

have a look at this mil standard where there is also a galvanic chart for atmospheric exposure:

http://www.wbdg.org/ccb/FEDMIL/std889b.pdf

S

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