Summary for brass tarnish prevention Discussion
Brass tarnish on tubular sleeves is the issue in this thread, with the manufacturer asking for a cost- and time-effective fix after a quick dilute sulfuric acid dip and ball burnishing. Keshava Prasad M suggests adding 1,2,3 benzotriazole (BTZ) at about 1% to the final chemical dip as a way to avoid tarnishing, and says to try it as a final treatment. A second reply adds a caution that brass can suffer seasonal cracking when stressed or exposed to ammonia, and that chlorides, sulfur, or ammonium in the environment can increase corrosion rates. The discussion therefore points to BTZ-based post-treatment as the practical anti-tarnish measure, while also noting that service environment and stress may contribute to the problem.
Q. We are component manufacturers for Automobiles, Defence and agricultural industries. Recently we started having problems with one of our brass tubular sleeves(25 mm OD x 35 mm length). They were being returned due to discoloration/tarnish. Is there a cost/time effective way to solve this problem. Currently our final operation is to ball burnish these parts after a quick acid dip (dil H2SO4). Please advise.
Thanks
Praj Amin
Component Manufacturer – Bombay, Maharashtra, India
2004
A. Dear Praj,
If you can think of having chemical dip as a final treatment, tarnishing may be avoided, by using an additive 1,2,3 Benzotriazole(BTZ)
⇦ on
or
Amazon [affil link]
in your chemical dip, the concentration may be 1%.
Just try out, Good Luck.
Keshava Prasad M
– Bangalore
A. Ref. a book — technica przeciwkorozyina-warszawa-1973 (russian trans)-page105 — brass may have what they call seasonal cracking, that may be seen if the metal is stessed or if there is ammonium (NH3) in the air. A high percentage of chlorides, sulfur, or ammonium in soil would increase rate of corrosion.
Khair Shishani
aircraft maintenance – Al Ain, UAE
A. Dear Mr. Praj Amin
The problem seems to be due to dezincification. Use of 1, 2,
3-benzotriazole (as suggested by Mr. Keshava) as corrosion inhibitor
(CI) is generally recommended. However there are several new and effective CI available. The usage condition (i.e. temperature, duration and concentration of CI etc.) is more important in all cases.
D. JAMAL
– Pune, India