What does this mean? Is the cadmium oxide 24g over a certain area? What do they

Question

What does this mean? Is the cadmium oxide 24g over a certain area? What do they mean by the formation? Can I use this to predict the total weight of the cadmium plating on a bolt? How?

7.18 CADMIUM COATING Cadmium is anodic to iron (Eid =-0.403 V and Ele =-0.440 V). Cadmium can resist a humid atmosphere better than zinc, but it has a far less protecting power than zinc. The most common method of applying cadmium coating is by electroplating. Cadmium plating is done in cyanide baths containing a mixture of cad- mium oxide and sodium cyanide to produce Na Cd(CN). The following is the formation: Cadmium oxide, 24 g Sodium cyanide, 75 g Sodium hydroxide, 15 g Triethoanolamine, 20 ml Nickel oxide, 0.2 g Current density, 5 A/dm²

Explanation / Answer

First of all let us understand what the bathing process is. An alkaline cynide bath is prepared by dissolving cadmium oxide in a sodium cynide solution at a suitable temperature. Then the metal part to be coated is submerged completely into this solution for a specific period of time. Once the desired layer of coating is achieved, the part is taken out of the pool.

Now, as aked by you, the bathing solution is prepared by adding the given amounts of components. It's like a recipe of making bathing solution. It does not mean that cadmium oxide is 24g over a certain area. It is the amount of cadmium oxide present in bating solution.

Secondly, the thickness of protective layer depends upon the time for which the part is kept in pool. From that you can calculate the weight of the coating by multiplying cadmium density to volume of layer.

Best of luck!

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