letter 53467

Surface Tension in Acid Pickling and Chemical Milling for Titanium

October 26, 2009

My company uses HF and Nitric to chemically mill parts. We also use the surfactant Dowfax 2A1 to control the surface tension. The control we have for the surface tension solution, when we test it, is that is must not exceed 50 dynes. I understand that high surface tension leads to only partially wetted parts and uneven chemical milling, but is there a problem with too much surfactant? I heard a rival company maintains their baths around 20-35 dynes, and I was curious if we should be less lax with our bath specifications to improve quality.

James Proestos
foundry technician - Albany, Oregon

Sir:
Just note to let you know that I use a surfactant in Hot Dip Galvanizing that provides a surface tension of about 30 dynes/cm at a concentration of 3 parts/10,000 of solution. If this product interests you, you can contact me as I am a supporting advertiser of finishing.com. You can see some of my responses in the Hot Dip Galvanizing section including a new rinse purification machine, methods, and aids. Originally I am from Portland.
Regards,

Dr. Thomas H. Cook, Galvanizing Consultant Hot Springs, South Dakota, USA