Where the
world gathers for metal finishing
Q&As since 1989


-----

How to analyze / control HNO3 - H2SO4 - NH4 - HF2 type desmutters?

For the pretreatment of aluminium for Electroless Nickel, we use a fluoride (NH4 - HF2) containing (nitric-sulfuric) acid mixture for desmutting. Until now we have not found a easy way to analyze and control the amount of fluoride in the bath.

Are there ways of doing this easy...? Special equipment might be considered, however we have very few persons to do a lot of work, so the method can not be very labor intensive... Any other suggestions for analysis/control for these types of baths are more than welcome! e.g. is the amount of Si or Mg in the bath determining for the quality of desmutting/pickling? Anything else?

Roy Orbon
- Netherlands
2000

---

Look back a few weeks in the letters section. There were several letters concerning this subject, especially topic #4626. No sense repeating it because it is here.

James Watts
- Navarre, Florida
2000