Corrosion of Ti 6 Al 4 V

[JTreglio]

We have a customer concerned about the corrosion resistance of Ti64, and would like to run some corrosion tests, such as ASTM B117. Does anyone know what a typical time to corrode for Ti64 is in an ASTM B117 test? How long does it take if it is Tiodized (alkaline anodized)?

Jim Treglio

 

[TVP]

Titanium and its alloys are essentially immune to general corrosion when exposed to seawater, including submerged applications. Table 5 of the following document has some data:

http://www.timet.com/pdfs/corrosion.pdf

Ti-6Al-4V should not corrode in a salt spray (fog) test such as ASTM B 117, unless there are many crevices, galvanically unfavorable couples, etc., or at least not in any reasonable amount of time.

 

[EdStainless]

It either takes a really bad surface condition with crevices and embedded metal, or higher temps.

 

[mshimko]

What's the application?

In general I concur with the statements above that Ti alloys are generally immune to most forms of corrosion i most environments. There are always exceptions, of course, but these "exceptions" are not what standardized tests are meant to assess.

 

[JTreglio]

The parts are used in marine undersea applications, so salt water resistance is most important. Temperature is not a factor.

Jim Treglio

 

[mshimko]

Under ambient temperature and seawater, the only issues I see are very tight crevices, and possibly embrittlement. I've seen the ELI (extra low interstitial) form to reduce possibility of the latter.

If you check out the various data books, you'll see terms such as "immume" and "nil" in seawater corrosion tests.