The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Nickel plated brass sheet is staining

March 13, 2009

Hello everybody,

I have a problem of stain onto brass sheet which are nickel plated:
- Brass alloy : Zn39Pb2
- Brass properties : laminated sheet, very bright, protected with a plastic film and an acid engraving is made onto the brass before plating
- Process :
- Ultrasonic soak cleaner : 2-4 min depending the polishing compound to remove
- Cathodic degreasing : 30 s - 1 min depending the dmÖ
- Sulfuric neutralization dip
- Bright nickel : 3 A/dmÖ / 6 min

First, the brass seems to be oxidized after sulfuric neutralization, we do a wood nickel strike to hide these marks and it is ok.
Second, I have some clouds onto the bright nickel but not on all part : from the batch, only 1 of 4 sheet has this mark.

We try a lot of parameters :
- we change the soak cleaner
- we put the sulfuric neutralization to the good concentration
- we check the bright nickel (Hull cell and sample plating to 3A/dmÖ): no cloud, pit or any nickel problem

My problem is : it is not a regular problem but some batches are ok without problem and some batches have 25% sheet with cloud problem.

Anyone has an experience or idea onto brass treatment and onto engraved brass treatment ?
Because I am very disappointed and this business is not good for me!

Thank you for your answer,

Nicolas Duthil
plating shop project leader - France

---

March 17, 2009

1. Try to add some peroxide (very small amount) into the sulfuric
2. You have lead in your alloy. You need a fluoboric dip prior to plating

Sara Michaeli
Tel-Aviv-Yafo, Israel

---

March 19, 2009

I THINK A ANDOIC CLEANING AFTER CATHODIC WILL HELP IN REMOVING CLEANING MARKS.
DO ANODIC CLEANING FOR 5 TO 10 SECONDS.
HAVE YOU DONE WATER BREAK TEST AFTER sulfurIC ACID DIP.
OR
A COPPER STRIKE BEFORE NICKEL PLATING WILL SOLVE ALL PROBLEMS.
REGARDS,

Ajay Raina
Ludhiana, Punjab, India