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topic 2704

yellow patches


(1999)

Respected sir,

I am facing one problem in silver plating Ours is a conventional silver plating bath contains 150g/l kcn & 25 g/l ag we have improved our acidconc of acid cleaning to 25%.Alkaline cleaning bath conc is also increased to8%.still we are getting yellow patches Our process sequence is as fallows hot soak(5min),anodic(3min)rinsing,acid cleaning,rinse ,copper plating(rochelle),cyanide dip,silver strike , silver plating ,rinse ,passivation (chrome) rinse hot rinse.

Please tell what could be the reasons. also please write us ideal conc of plating bath & cleaning conc to get quality finish.

Thanks regards.

A P Barve.

Avinash P Barve



(1999)

Hi,

First you have to check your brighteners if you don't use you must.

You can give the pice a niquel coated after the copper

The ideal bath of silver is 125 to 150 gr/L. kcm 26 to 32gr/L. Ag

Please if you have any result, post it.

Jamyl.

Jamyl D'Angelo
Lima Peru

(1999)

You might want to try turning off the heat on your final rinse. On matte finish cyanide silver this is a must to eliminate yellowing. It takes longer to dry the parts, but the appearance is much better. Also, are your spots appearing after you handle them. This can also be a trouble spot.

Phil Pace
- Tulsa, Oklahoma


(1999)

DEAR SIR, ADVISED PL TO USE BEST QUALITY OF brighteners AND MAINTAIN PROPER CONCENTRATION OF brighteners. UTILISATION SYSTEM OF CYANIDE WILL SOLVE YOUR PROBLEM.

SHAH JANAT
AHMEDABAD/ GUJ/ INDIA



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