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Process sequence

2004

The component is heat radiator used for drying the cloth in hotel ( Hot water circulate in the radiator). The base metal is M.S> with Silver brazing on the corner. The plating requirement 15 - 20 microns copper and 25-35 micron nickel.

My question is: Please suggest complete process sequence ? The material is exporting to other countries from India through sea route. The problem faced corrosion spread over all areas of the component and peel off.

The process sequence we are adopting are :

Soak Cleaning
Soak cleaning
Anodic cleaning
Cascade Rinse
Electrolytic Etching ( sulfuric acid)
Cascade Rinse
Neutralization dip ( Cyanide)
Cyanide Copper plating ( thickness 2-4 microns)
Cascade Rinse
Acid Dip sulfuric acid
Cascade Rinse
Acid Copper Plating ( thickness 12-15 microns)
Cascade Rinse
sulfuric acid Dip
Cascade Rinse
Semi Bright Nickel Plating ( thickness 15-20 microns)
Bright Nickel plating ( thickness 10 microns)
Dragout
Cascade Rinse
Chrome Plating ( thickness 0.3 microns)
Dragout Neutralization
Cascade Rinse
Hot water
Dry

Regards,

N.Ram
Plating shop - New Delhi, India

Cyanide copper thickness seems too thin for mild steel further exposed to acid copper. Where is the separation taking place, the base MS, or delamination within different plates?

Guillermo Marrufo
Monterrey, NL, Mexico
2004

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2004

Mr Ram,

Possible reasons:

1) The parts are not dry. Possibly damp parts are packed.
2) The packing paper is acidic . Check the rinse from the paper if it has an acidic pH.
3) The chrome thickness is not really the 0.3 microns you imagine it is.
4) Is the last Hot water actually HOT. 90 centigrade is required ALL the time 60 to 90 seconds timed dip. Actuals need a check.
5) If possible replace the Cyanide copper with a Woods Nickel strike of 2 to 3 Microns. Ensure the Bright Nickel solution is not full of organic impurities.

Lastly:

If the plating thicknesses are actually as you have stated , ACTUALLY measured thicknesses please note, the corrosion so quickly is not possible. I suggest you ask your chemical supplier to verify:

Thickness of the Nickel.
Step test
Chrome thickness
Presence of Sulfur in SB Nickel.
Presence of organics in bright Nickel.

Good luck

Asif Nurie [deceased]
- New Delhi, India
With deep regret we sadly advise that Asif passed away on Jan 24, 2016

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