48074

Hard chrome plating problems [Norway] 

March 6, 2008

We have, in our workshop an chrome bath wit about 6000ltr chrome acid, with 12000 amperes available.12V supply
The main problems is Grey shadows in the chrome layer, and also pittings.
The chrome is also not so hard as it used to be.
The materials this appears on is regular ST52.3N and SIS 2387, all grinded and polished before chrome plating.
We also do chemical cleaning and activation on the rods we chrome.
We have checked the power suppliers an also the acid but we can not find out what is wrong with this.
We would be really happy to hear form someone with deep knowledge in hard chrome plating.

Best regards
Anders Aronsen
General Manager.

Anders Aronsen
Plating shop/hydraulic repairs - Trondheim, Norway

Hey there,
you did not write anything about your latest analysis results. Also, are you using a catalyzed bath, than you should also consider letting an analyze.

Good Luck,

Dominik

Dominik Michalek
- Mexico City

Hello Anders,

Make a analyse on the cromic acid for contaminents like iron, aluminium, copper, trivalent chrome. Control the anodes so they are active. I think the ratio betwen chromic acid and sulphate is wrong.

Read my article about chrome plating in the library here on finishing.com

Regards

Anders Sundman     surface finishing engineer Sweden

Hi , I'm a hard chrome plater and had very similar problems when I started , the pitting could be many things from , the parts being porous , poor cleaning and etching , and even the wax used for masking .

Sometimes , if your wax is dirty or contaminated , you can see rust ( like pitting ) through the glyserine after you have done the first part of the masking .

Also leaving work in the hot wax too long can cause pitting problems if your wax is dirty. (some people de-mask in the wax tank therefore contaminating it with chemicals and water etc.... a new wax put an end to my pitting problems , simple but not something people think of!!!

As for your grey discolouration , have you had an analyse of your solution ? are the anodes clean , is the vat stirred after being topped up ( cold water sits on top and causes burning to the part ? ( sounds silly but a guy from another plating firm visited my factory and asked why I stirred the vats - then he said his parts looked grey and horrible !

The newer the solution , the brighter the finish and also the chrome is harder , but it does dull down with age , maybe its time to renew yours ?

J Smith
- Essex, England

Could be:

-shadowing from an edge
-etching too long, not long enough
-etching current too high
-plating current too high, calculate using L*D*3.1416 for 1thou an hour plating current.
-temperature too cold

could be a number of things, guide me through your plating process and i may be able to help you

Mike Hunt
- Perth, WA, Australia