plating, anodizing, & finishing Q&As since 1989
HF replacement/reduction for deox of Aluminum casting
I am currently using a Nitric/HF solution for Aluminum casting deox. Is there a way to eliminate HF from the solution? I know that it would be pretty tough to find a replacement of HF to treat Si, but do you recommend any additives to the solution to reduce the amount of HF required?Sally Nguyen
- Dallas, Texas
HF is viewed differently from one person to another. My feeling is that 70% is very dangerous to handle as it is terribly unforgiving. 50% is much less of a problem and 35% would come close to being handled like most other acids. The nice part is, you do not have to use HF to get the fluoride ion. You can use ammonium bi fluoride which is a crystal. You end up with a same F ion concentration so is minorly hazardous, only slightly more so than just a plain Nitric Acid burn.
Available from many sources. Obviously cheaper if bought from someone that sells raw chemicals than from a specialty process company as they have to have their markup and repackaging cost.James Watts
- Navarre, Florida
Our company produces a spent nitric/HF acid from the etching of pure silicon used in the semiconductor industry.
Some companies are using a nitric/hydrogen peroxide solution to etch Si. You may wish to try a similar solution for Al. If you need to neutralize the acid then lime would precipitate the fluoride but would also leave a dilute calcium nitrate solution.
If you have interest in our spent nitric/HF acid I could send you a chemical assay, a sample and arrange to delivery an ongoing supply of acid to you.Tom Mackey
- 7800 Mitsubishi Lane, Theordore, Alabama
Hi It¥s not easy to take away the nitric/HF but we have been selling a combinations of two deoxidizers for some years now that has replaces the nitric /HF deoxidizer on high Si aluminium alloys. Its a combination of a special peroxide deoxidizer and another deoxidizer based on two acids and fluorides. We found after several trials that it was possible. Thoose two deoxidizers need more close control then the nitric/HF deoxidizer. If this could be interesting for you. RegardsJorgen Pettersson