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


-----

Chemical Removal of Glass Bead Residue from Stainless Steel

I need to TiN coat stainless steel parts as a final step in manufacturing. The parts are matte finished using MIL spec glass beads prior to the TiN coating. A number of manufacturers have attempted to coat these parts with limited success. It seems that we are leaving glass residue on the surface of the parts. Up to now, we have been mechanically removing the residue, but this detracts from the matte finish we are trying to achieve.

I need to know if anyone has a suggestion on a method of removing this residue chemically without adversely effecting the stainless steel base material.

Jerry Szostek
- Barberton, Ohio USA
2000

---

Jerry:

There are vibratory processes available that utilize reactive chemical compounds that are very effective at removing Silicon Dioxide from surfaces of steel, stainless steel, titanium, and a whole range of Nimonic alloys. The benefits of the process are that the surface is clean and the grain boundaries are generally open. This promotes improve coating adhesion. Standard vibratory equipment is used and the process time is relatively short. There is chance that the Silicon Dioxide can be removed, and maintain an acceptable matte finish. Only testing will tell. Good luck, Bill

Bill Boatright
- Raleigh, North Carolina
2000

I do not know of any chemicals other that hydrofluoric acid or ammonium fluoride that can dissolve silicon dioxide. These are routinely used in Si-semiconductor industry. May be similar bromides or iodides could do the same. HF is a very fast dissolver, the other one is very slow.

Mandar Sunthankar
- Fort Collins, Colorado
2000

Especially before PVD coating we can offer method of electrolyte-plasma-polishing/ It can take place under high voltage (pulse DC >200 V) in neutral (pH 5~8, C= 4~10%) solution of inorganic salt. We have decisions for most popular metals and alloys. Regards

Gennadzy
- Minsk, Rep. of Belarus
2000

---

If it is some sort of very fine silica powder residue, try a hot sodium hydroxide bath, maybe even in an ultrasonic bath. The hydroxides will not affect the stainless, and silica is weakly soluble in high pH solutions. Rinse well in deionized water.

No real problem with hazardous waste either. When the solution is cool, carefully pour it down the drain and rinse with a lot of cold water; it will help to keep the plumbing clear.

Dale Woika
Surface Conversion Sciences - Bellefonte, Pennsylvania
2000

---

2003

Jerry:

DEAR SIR,
WE SUGGEST YOU CLEAN UP THE RESIDUE WITHOUT SCRATCHING THE SURFACE BY USING walnut shell media [on eBay or Amazon] BLAST CLEANING. IT IS A SOFT MEDIA FOR BLAST CLEANING REGARDS,

RAJESH PATEL
- JAMNAGAR,GUJARAT, INDIA