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Bath control for chemical milling of Ti-3Al-2,5V

Dear experts,

I am working in a company that produce seamless tubes, and as a new product we are trying to produce Ti-3Al-2,5V tubes from 6 to 25 mm of diameter. As a part of the process, we need milling chemically with a solution of HNO3/HF the inner and the outer surface of the tubes. We have limitations to invest money in sophisticates devices to control the bath so we have to use some traditional method to control it.
Now the questions:

Which are the parameters to control (concentrations, acidity, titanium in solution, temperature..)
Which is the best way to control them (without expensive equipment)
It is possible the control of the roughness changing some parameters

Thank you in advance and any other suggestion will be welcome

Diego Delfino
materials engineer - Buenos Aires, Argentina
June 2, 2010

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Diego-
You will want to titrate for the nitric acid content, but rather than analysing for the HF it is better to make adds as necessary to maintain a consistent etch rate. Temperature has a significant effect on etch rate, so you will want to keep the temperature constant by either heating or cooling the bath to a set temperature instead of relying on your ambient conditions.

If you search on this website, you will discover lots of other information from previous posts. Good luck.

Jon Barrows, MSF, EHSSC
GOAD Company

Independence, Missouri

June 3, 2010