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Benjamin Gradler
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16 July 2009 08:21 I found this information on re-chromating magnesium castings which might be helpful to those with the balls to give it a go: Should you consider chromating yourself the chemicals are :- 1) Magnesium diachromate (bright orange) 2) Manganese sulphate (white) 3) Magnesium sulphate (white) Please check your local area and suppliers regulations for the use of these chemicals. Add to 1 Imperial gallon of warm water 1 lb of orange chemical and .5 lbs each of the white chemicals stir well to dissolve completely. Plastic or aluminium containers, a plastic dustbin works well for larger items. Rechromating old castings You must first clean the existing chromate off, this is best done by blasting with aluminium oxide grit. do not use sand,glass,steel or cast iron media. Or boil in caustic soda. Use gloves as finger marks sometimes stops the chromating working. Chromating can be done cold between 4 to 12 hours but if you heat the solution to about 50 degrees C. Do not boil. The process takes about 15 minutes but do it in a well ventilated area. The mix will go active when it is working with small bubbles coming to the surface and even produce an orange froth depending on the preparation of the casting. The colour should be dark brown to black when the process is complete, the castings must be washed well to remove the chromating liquid. If you leave the castings in too long you will get a black powdery coating on the casting which will need hot water cleaning with a stiff brush to remove. After some time the mix will lose its effect especially if done hot, in which case throw away and wash the container for a fresh mix.
 
Benjamin Gradler
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17 July 2009 10:06 Here is a company in California USA that sells a kit for magnesium conversion coating. They have a website at www chemical supermarket com.

I have left out the abbreviations for the web address because posting here seems to be sensitive to html codes in postings.

Anyway it says the treatment kit is commonly known as Dow7 and leaves a charcoal grey finish on magnesium alloys.

The company has a lot of interesting products that apply to the aviation trasportation and electronics industries.
 


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