The authoritative public forum
  for Metal Finishing since 1989
-----

Plating of brass with electroless nickel and gold

My question is two part, 1st problem: Involves the plating of low lead brass with electroless nickel followed by immersion gold plating then heat treat.

I am using a citric acid ⇦this on eBay or Amazon [affil links] to treat the brass prior to electroless nickel, the product is then processed through a cleaner with 85-95% sodium bisulphate and 5-15% sodium fluoride. Then immersion gold plated, and heat treated at 450F. The product is cylindrical in shape with a hole in one end where a pin is inserted, the OD of the part is crimped to hold the pin. The problem on occasion has been that the gold tends to flake off the face of the part on the hole end.

2nd problem: If the above product when tested produces gold flaking it is sent for rework. This rework is not always if seldom effective. The process involves stripping the gold from the part leaving the nickel plating on the brass substrate. The part is then processed through a 50 % HCl solution for two minutes, nickel flashed, through the 50% acid again, gold plated and then heat treated. This is not producing satisfactory results. In both processes the product is rinsed between steps.

I would like to hear from anyone who has knowledge or experience with this problem.

Thank you,

Robert Sachs
- Morrisburg, Ontario, Canada
2003

---

IN the case of the gold not adhering, I suspect nickel passivity (platers term for oxide). Try a Woods Nickel Chloride Strike after the electroless nickel and an acid gold electroplated strike then the immersion gold. Immersion gold does nothing for removing nickel oxide but it will lay down on top of it and not stick And if the nickel is not sticking to the (low) leaded brass then insert a step of 50% Fluoboric Acid. Lead on the surface of the brass forms insoluble salts with chlorides, fluorides, and sulphates. These insoluble salts bridge with plate and then stress and flake off.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003