Where the
world gathers for metal finishing
Q&As since 1989


-----

Tin Plating stains on Copper

April 22, 2011

I am applying plating on Brass and Nickel however some stains appear after tin plating is done. Stain looks like the foam bubbles are attached to the parts plated, leaving very visible white circle stains.

Can you help me with this?

Regards

Sergio Samaniego
Mexicali, Baja California, Mexico

---

That is the typical stain from the tin solution surfactant not rinsing off. You have to go into an alkali and then rinse again. Most vendors have a special product for removing this tenacious film. Try a non-etch mild alkaline cleaner, or just 4 oz/gal sodium carbonate / washing soda [affil links], then rinse again.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

First of three simultaneous responses -- April 25, 2011

---

Second of three simultaneous responses -- April 25, 2011

Hello,
Is there a possibility you may have a previous surface or plating that is already porous? In any case you may want to inspect the surface right before entering the tin bath with a magnifying glass. If the surface is free of pores you may need to purify your solution and check with your chemical vendor what surfactant is compatible with their chemistry and its optimum concentration. If you find previous porosity, you need to identify the origin. Good luck,
G. Marrufo-Mexico

Guillermo Marrufo
Monterrey, NL, Mexico

---

Third of three simultaneous responses -- April 26, 2011

1. Do not plate tin directly on brass. You need a copper or better a nickel layer in between.
2. After rinsing the parts following the tin plating, dip in a slightly alkaline solution, then rinse again

Sara Michaeli
Tel-Aviv-Yafo, Israel