Etching Titanium for Anodizing

Etching Titanium for Anodizing

 

Question From our Customer In Sweden

“I am trying to etch titanium medical devices using an Ammonium Persulfate and Ammonium Bifluoride blend. The pH immediately after mixing was around 4.0 – 5.0.  Then I heated the mixed solution after stirring to approximately 120F and dipped the test piece into the solution but nothing happened. I waited a couple of minutes and increased the temperature, but still nothing happened.  What am I doing wrong?” 

Answer

I am wondering if the problem is in your evaluation of the etching results.  It sounds like your evaluation was empirical based on visual observations.  I assume that you were looking for some off-gassing to occur in the bath. Etching titanium for anodizing is not always a visible reaction like etching aluminum. Also etching titanium that is raw may not change much in appearance. You may be etching the part just fine and not notice it.  Try evaluating the process by using a different method.  Here are two ways to do this:

  1. Etch parts that are already anodized and colored – you should see a color change.
  2. Etch the parts and anodize them. Compare the results – are they better with or without etching?

 

You could go even a step further… evaluating the etch rate by taking a coupon of 6-4 titanium of known area and weighing it before and after etching.  You can possibly accomplish the same based solely on measuring the thickness of the coupon and determining the difference in thickness.

 Response From the Customer

“Thank you for your help and advice. You were right, I only did a visually inspection. Today, I measured a piece before and after etching and discovered a change. So, I think we have a reaction even if we can’t see it as you thought.”  

Etching Titanium for Anodizing Implants

Etching Titanium medical devices can be tricky, it will take some trial and error, but the results can be well worth the effort.

How to Anodize Titanium