Cobalt and Chrome (6, 4 and 3+) Plating.

Introduction: Cobalt and Chrome (6, 4 and 3+) Plating.

About: I am a part-time hobbyists biotechnologist with a photonics background. I also have a YouTube channel too. I work part-time too.

Hello, Instructables Viewers I am showing with graphite bars how to plate cobalt hypochlorite over copper that appears red but turns yellow that can be lacquered with Urethane and using chromate Normal and high concentration sodium dichromate with Magnesium sulfate (forms a buffer) in solution to plate steel. Low concentrations of chrome 6 salts create yellow-orange metal. High concentrations over 20 g a L produces crystals of chrome and iron that form a mixture.

Step 1: Making Cobalt Chloride HCl 10 Percent Solution.

First, for the cobalt chloride make sure it quite pure more than 99 percent for this to work. Add to 2 L of tap water about 10 g of cobalt chloride and add 10 percent 200 ml of HCL (Hydrochloric acid) clean no impurities to your solution.

Use a carbon electrode for Positive and Negative for a wire with copper pipes, etc on it. Let it run at 125 mA 3-4 volts for 20 minutes max. Keep in mind some chlorine gas is generated and also produces Cobalt hypochlorite Co(ClO)2 as well. It bleaches the coating too.

See first page for pictures.

Step 2: Chrome Solution Prep. Low and High Concentrations.

The polarity for sodium dichromate with steel does not matter for this it does for the cobalt tho. If you reverse the voltage with cobalt and carbon electrode then carbon will plate to copper.

For the low concentration to a 2 L bowl or flask add 5 g of sodium dichromate to 10 grams of magnesium sulfate add a copper pipe for + and attach a wire to the stainless steel. This solution is corrosive to metals so make sure the wire clip does NOT TOUCH THE SOLUTION EVER.

For high concentration add 20 g of sodium dichromate to 2 L tap water and 5 g of magnesium sulfate do the same as the low concentration.

After drying for a day both cobalt and chrome type must be Urethane coated.

Step 3: Final Results Urethane Paint of Cobalt Metal and Metal Material With Urethane.

Since Urethane is required please get some in Mineral spirits. The final cobalt images with coat are here. Also it prevents the chrome crystals and the cobalt plating from coming off.

Cobalt chloride solution is toxic, corrosive and level 2 cancer causing. Please wear PPE and use Lye and H202 to convert the cobalt into Cobalt (III) hydroxide. Adding sodium dichromate to either an acid + sodium thiosulfate or sodium metabisulfite works very well to convert the chrome 6+ and chrome 4+ into a safe chrome 3+ then add the lye.

Also, solutions of sodium dichromate are level 2 cancerous, toxic and corrosive so PPE (especially Faceshield with it is required). Even tho it pH for 1 mole is 4.8 the chemical induces burns by attacking DNA, cells structure and mRNA.

All these products MUST go to the eco-center for safety they are slightly toxic now.

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    3 years ago

    If bleach and chlorine is added to 10 g cobalt chloride and H202 and lye is added you can get these types of results pretty green-brass colored plates of copper. 1 ml of conc bleach is added to the cobalt chloride salt. (5 percent NaOCl) at 1 ml is recommended.


    4 years ago

    Sodium dichromate recommended over Potassium dichromate due to solubility in water, etc can be easily bought 200 g for 20 dollars US on eBay. Keep in mind some countries may not be able to buy it --- dangerous product.

    Even if stored from 1990 from Russia it does not degrade in storage so that not an issue. Magnesium sulfate can be bought at any Pharmacy.


    4 years ago

    I recommend pure cobalt chloride over cobalt carbonate and Hydrochloric acid. You may need to search a lab science supplier that sells to indviudals tho.