Ferritic contamination of titanium 1

• Jun 27, 2008

1
• #2

bruv

Materials

Feb 19, 2002

239

GB

You should be following something similar to ASTM A380, "Standard Practice for Cleaning, Descaling and Passivation of Stainless Steel Parts, Equipment and Systems".

Section 7 (Inspection after Cleaning) gives a couple of tests for detection of iron contamination. We have used the Ferroxyl Test very succesfully on titanium alloys. Application of the solution was carried out with a spray bottle. Removing surface iron contamination can either be done by brushing off, washing off or ultimately by grinding out and welding up the hole (if allowed).

We heven't needed to do any stress relief, so I can't tell you what might occur with the test. Try deliberatly contaminating a piece and testing after H/T, and let us know what you find.

 

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• Jun 27, 2008

• Thread starter
• #3

antoine66

Materials

Jun 2, 2008

6

FR

Yes, we use one of the tests specified in A 380 (which also gives info about copper sulfate test, we also can use phenanthroline test).
My concern is that I heard that once heated, the contaminant parts migrate into the titanium and cannot be detected any more, while hampering the corrosion resistance of the titanium. This may be the reason why some engineering specs (AMOCO, KVAERNER, etc..) are asking the cleaning to be performed before any HT. I would like to find somebody with some feedback about this.

 

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• Jun 30, 2008

• #4

limey1

Mechanical

Nov 15, 2007

103

SE

Im not an expert on corrosion but, wouldnt the Ferroxyl test also show positive if there is a thermal oxide layer?. This has been confused in the past, with Iron deposits. Or are they one of the same?.....Just throwing it out there chaps!

 

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• Jun 30, 2008

• #5

EdStainless

Materials

May 20, 2004

16,357

Waukesha WI USA

After heat treatment you could see Fe contamination if you pickled the parts. The Fe will for an intermetallic compound with the Ti. This is brittle and has poor corrosion resistance.

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Plymouth Tube

 

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• Jul 1, 2008

• Thread starter
• #6

antoine66

Materials

Jun 2, 2008

6

FR

About thermal titanium oxide, I do not think Ferroxyl test will react because it is specifically intended to react with iron. If some iron oxide is still present on the titanium surface, we may find it but if it diffuses inside titanium thickness, we may have trouble to detect it.

It is true that we may see Fe contamination when pickling the parts, however, this is not an option for us because we are manufacturing titanium bonded steel plates and the pickling solution will attack the backer steel.

I also read in a paper that iron contamination could favor hydrogen absorption of titanium, which also hampers corrosion resitance. Anybody to comment?

 

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