The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Preventing Aesthetic Corrosion of Brass

2005

We currently manufacture an aesthetic valve made from brass 360. It currently receives a thin layer of electroless nickel to pretty it up and prevent corrosion. The problem is that the part has a lot of thread that is required to be masked, thus the plating of the part ends up costing us 7-8 dollars in the quantities that we order. What we'd like to do is find a process that will be much cheaper, 25% or less of the cost of the EN plus masking, while still providing adequate corrosion resistance. Legally, we cannot have metal buildup on the threads (hence the masking), though other substances may be acceptable as long as they are compatible in a concentrated oxygen environment.

The part itself isn't exposed to harsh environments, just occasional exposure to ambient weather conditions for short periods of time....but I've been told that our parts that have just been "bright dipped" will eventually show some signs of discoloration.

Does anyone have any suggestions as to other processes we can look into? I stumbled onto the name benzotriazole ⇦ this on eBay or Amazon [affil links] but I have no idea what it is or how effective it is in comparison to a bright dip, or whether or not it ignites in oxygen.

Matthew Yavorsky
Medical - Chatsworth, California, USA

---

2005

Dear Mr.Matthew Yavorsky,

1,2,3 Benzotriazole is an additive that may be used with your bright dip. It just forms a very thin transparent(?) layer on the surface of the components. This is resistant to corrosion (Especially marine atmosphere).

Keshava Prasad M
- Chennai, India

---

Thanks Keshava,

Does benzotriazole build up a layer on the outside of the brass (Like a plating), if so what are the typical thicknesses used. Also, is thread masking typically neccesary when using it?

Matthew Yavorsky
- Chatsworth, California, USA
2005

---

2005

Dear Mr. Matthew Yavorsky,

Well....I am not much exposed into the theory of Benzotriazole, but its a known corrosion inhibitor especially for copper and copper alloys, people have been using it(You can get many expired patented formulae which involve Benzotriazole, if you get into Books for Metal Finishing)
The researchers say, it reacts with Copper Ion (Cu I & II)
and forms a polymeric complex which prevents further oxidation of the metal. Thickness may be very less (may be even less than a micron.)

It is soluble in alcohols. May be 1 - 2% is soluble in water. I worked on it for Bright Dip Phosphoric-Nitric Mixture and 0.5% of Benzotriazole (water dissolution)
For some fittings made up of Brass. It gave me good salt spray results of 96 Hrs (5% NaCl).

Hope this helps..

Keshava Prasad M
- Chennai, India

---

2006

Matthew:

I agree with Keshava that Benzotriazole ⇦ this on eBay or Amazon [affil links] is your best bet. The coating thicknesses are very low (microns at thickest) and can be controlled by concentration, temperature and dwell time for your parts (the longer in the bath, the thicker the coating). A company I used to work for sold an off the shelf product called Coppershield 860 which could be easily mixed with water. You only need very small concentrations to be effective, so it's not a huge expense. I believe that Henkel Surface Technologies now owns the Coppershield brand name, but they may have changed it. I'd check with them or one of several other metal products companies such as Chemetall Oakite or PMC Specialties.

Timothy McGrady
- Lansing, New York