Which Ti grade is most compatible to water saturated with chlorine and salt traces 2

[AZMAG28]

Hi glad to be member of this Forum.
Ti Gr12 has been used to construct pressure vessel to contain water contaminated with chlorine and some salt traces. Ti Gr 12 is potential of having crevice and pitting corrosion after 70 Deg. C. any suggestion of alternative or special care?

thanks

 

[EdStainless]

Have you looked up the Timet corrosion tables?
Who told you that Gr12 might pit in saturated NaCl at 70C? The tables that I look at warn that at pH<3 and temp >100C Gr12 would corrode in saturated NaCl with free Cl. How much Cl do you have?
The next step up in corrosion resistance is Gr16.
The other option is to stay with Gr12 and keep the pH up a little bit, anything over 4 should be plenty safe.

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P.E. Metallurgy, Plymouth Tube

 

[AZMAG28]

Thanks Ed. I did some investigation and found that the pH is 2 and occasionally can reach 1.5. Looks Ti Gr 12 may not survive and what about Gr 16?

thanks

 

[EdStainless]

Yes, gr16 would be the next step. it gets expensive (alloying and lower strength) but it will tolerate the conditions.

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P.E. Metallurgy, Plymouth Tube

 

[HBMetals]

I think I have a technical literature which says Ti-0.5Pd (Grade 7 titanium) is a TYPICAL crevice-corrosion-resistant titanium material for industrial application with Cl ion ≈ 20%, PH2, 120°~130°C. The application is concentrator equipment in salt purification. Due to the large size, just upload a piece of screenshot of it.

Generally, Gr.1, Gr.2, Gr.3, Gr.7, Gr.9, Gr.12 are commercially available due to the comparatively low cost.

www.metalspiping.com

 

[EdStainless]

Recently there has been a movement to the low Pd grades in place of the older high Pd ones (16 in place of 7). They work just as well in most environments and don'T cost nearly as much.

With Gr7 the 0.5% Pd costs more than 5x as much as the 99.5% Ti does.

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P.E. Metallurgy, Plymouth Tube

 

[HBMetals]

Sorry that there's a typo. It should be Ti Grade 7 "Ti-0.15Pd". The nominal composition of Grade 16 is "Ti-0.05Pd". They have identical mechanical properties. However, compared to Gr.16, Gr.7 is more often applied in corrosion applications since there are more approved engineering experiences or technical literature. If you ask fabricators, most probably they will recommend Gr.7, since Gr.16 is hardly seen in the market. This is why it is commercially more competitive from another point of view.

http://www.metalspiping.com

 

[EdStainless]

For most construction in the last 15 years people would have used Gr16 in place of Gr7.
The lab test data is nearly identical and the price difference is significant (Gr 7 is more than 2x the price of Gr16).
If people want to stay with old alloys simply out of tradition then let them pay, but the data says otherwise. That is why Gr 16 was invented.

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P.E. Metallurgy, Plymouth Tube