Electroplating silver onto chromium surface.. help?

[shsy]

I am required to plate silver onto a sample with a plastic base coated with copper, followed by Nickel, then Chromium for a customer. After electrocleaning, I acid dipped in 10% H2SO4, and after plating silver, the silver layer peeled off. I tried acid dipping with 50% HCL and 25% HCL instead, but my sample ended up hazy. What should I do?

 

(There's nothing wrong when I plate silver over nickel using 10% H2SO4)

[John Cuthber]

Electroplating is often as much an art as a science but one thought that struck me is, can you plate nickel onto the chromium, then plate silver onto that?

[shsy]

Electroplating is often as much an art as a science but one thought that struck me is, can you plate nickel onto the chromium, then plate silver onto that?

 

 

There is already a layer of Nickel underneath the chrome. Anyway, I just found out that because chromium is like a preservative layer, so it will be very hard to activate and plate something else onto the chrome surface nicely. Which explains why silver peeled when I used H2SO4 and I couldnt get a nice finish with HCl

[John Cuthber]

Can you remove the chromium selectively?

Anodic oxidation in a strong base might remove the Cr and leave you with Ni which you can plate.

[Enthalpy]

Somehow I imagine the spontaneous chromium oxide layer hampers electroplating, and this should improve with nickel, yes.

 

Why electroplating silver? There are autocatalytic processes that deposit nice brilliant silver on any surface, like glass.

Edited September 2, 2011 by Enthalpy

[Delphi]

Hello everyone. My first question is Why do you want to plate Silver over Chromium? What is the final result you wish to obtain? I do electroplating for a living, and these are the questions I always ask my clients. Lets assume for a moment you wish to make the Chrome finished part, electricaly conductive for subsequent soldering and you are not that concerned about cosmetics.

 

Wire the part using electrical grade copper wire. Durring the process be sure not to touch the surface of the part as the oils in your skin will contaminate the surface. ALWAYS USE PERSONAL SAFETY EQUIPMENT (GLASSES, GLOVES, ETC...)

 

1) Strip Chrome using Reverse DC and 10 oz/gal NaOH solution. Steel cathodes are frequently used. Only takes a few seconds (20- 40). The Chrome layer is vary thin about 40 microns.

2) Rinse the part vary well in clean running water.

 

3) Clean again using soap cleaner (No current)

 

4) Rinse again in running DI Water.

 

5) Activate in 20%v/v H2SO4 for 30-60 seconds.

 

6) Rinse again. Be sure ALL ACID IS REMOVED. DO NOT TOUCH THE PART.

 

There are two methods to use;

 

1) Brush Plating. Using a cotton swab. Swab a solution of 1oz/gal Silver Cyanide solution on to the surface of the part to be coated. Coating will occure almost imediatly. continue over entire surface. Rinse with running water. REMOVE ALL TRACES OF CYANIDE, BY WASHING IN RUNNING WATER!!!!!

 

 

2) Submerge part in a 1 oz/gal solution of Silver Cyanide and apply 0.5 a DC current for about 30 - 120 seconds (more time the greater the thicknes).

 

NOTES: ALWAYS RINSE PARTS THOUROGHLY!!!! WHEN YOU THINK YOU'VE RINSED ENOUGH.....RINSE ONE MORE TIME!

 

 

"My spel check is not working yet"....sorry everyone....I will fix it ASAP.

 

What your experiencing is Ionic contamination. You should use NaOH with a SMALL Revers current to strip the chrome. Then go into your electrocleaner. Avoid using HCL. Use 10 -30 % H2SO4. Then silver plate. Just a small amout of Chromium contamination will prevent the silver from sticking.

 

 

What I have done in the past is after stripping the chrome and cleaning it was to place it back in Bright nickel tank for a few minutes. Then continue with silver plating.

[Delphi]

You have Ionic contamination. Nickel is kinda difficult to activate. What I have done is to lightly electroclean the part, then acid dip, then immedialty go into your bright nickel. just for a few second (10 - 30). Be sure to rinse the parts quickly and thouroughly avoiding any acids. Some times you may have excessive brightneres or wetting agents in the Bright Nickel solution those agents. Those agents work well in the nickel bath and the parts may come out looking beautiful, but when exposed to HCL or H2SO4 cause hazing when silver plated.

 

So just rinse quickly and thouroughly after nickel and go directly into your Bright Silver.

 

There are some really good activators but the most effect are cyanide based. These tend to be expensive to haul-out. I found it most cost effective just to put the parts back in my nickel tank for a few seconds. This seems to activate them very well.

 

I know there will be those "book-read" few that will say it cant work, but I found that no one has told this to the "parts". Those same few are those who claim it is mathamaticaly impossible for bumble bee to fly (but no one told the bee).

 

 

I am required to plate silver onto a sample with a plastic base coated with copper, followed by Nickel, then Chromium for a customer. After electrocleaning, I acid dipped in 10% H2SO4, and after plating silver, the silver layer peeled off. I tried acid dipping with 50% HCL and 25% HCL instead, but my sample ended up hazy. What should I do?

 

(There's nothing wrong when I plate silver over nickel using 10% H2SO4)