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ENP on Brass Components: No coating build up

March 25, 2009

Hi Experts.

Thanks in advance.

We have been doing Electroless Nickel Plating (Mid P)on (Leaded) Brass components since 2 Years. Now all of a sudden we are unable to coat on the components.

The procedure:
Degreasing - 2 Rinses - Electrodegreasing - 2Rinses - Activation - 2 Rinses - Electroless Ni Plating (i.e. when we immerse the components in the bath the components made cathodic and SS Tank is made anodic for 30 seconds)- 3 Rinses.....

We could not find any deviation in the process. But we used expired chemicals (expired in the month of Oct 08). We use De - ionized water. While checking we felt that no possibility of Nitric Acid contamination ( we passivate the tank with Nitric Acid)But there is no evidence for that.

The issue is this has been running since 2 years without any problem...

Thanks again for your help.

Prashanth TN
Plating Engineer - Chennai, Tamil nadu, India

Hi

I wanted to add up one info..

The expired chemicals are checked at the supplier's laboratory and okayed for production.

sorry for missing the info..

thanks...

Prashanth TN
plating engineer - Chennai, India

Plating with expired products is always problematic but I think that your problem is that you are plating directly on brass .If you have more than 3 turnovers probably you introduce some lead from the brass, inhibiting your bath.
I recommend to do a copper strike before the electroless

Ricardo Burstein
Bnei Berak, Israel

What happens when you plate a steel part?
If it is OK, it means that the electroless solution is OK.

As for plating on brass - brass, unlike steel, is not autocatalytic in EN solution. The best way to ensure good adhesion and coverage is plating a nickel strike layer prior to the EN.

Leaded brass always needs a dip in fluoboric acid (5-15%)

Sara Michaeli
Tel-Aviv-Yafo, Israel

Apparently your bath is contaminated or over stabilized. There are other substances that slow or kill the reaction besides nitrates from the acid leach, like lead, copper, chrome, etc. A dropped part in the tank may have dissolved. The tank walls or racks could have dissolved. Depending on the severity of the problem, you may have to dump the bath and prepare a new fresh bath. In the future, if you intend to keep plating over leaded brass, maybe you should consider a proper pretreatment with fluoboric acid and perhaps a formal initial strike of electro nickel in another tank instead of the electric kick.

Guillermo Marrufo
Monterrey, NL, Mexico

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