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GALVANIZING

 

After anodizing aluminum will naturally move on to the next electrochemical experiments, the benefit fingertips and electrolytic bath, and a current source, and a switch with dimmer. In these experiments, we will extract the metal from the solution and apply it to the surface. This process is called the galvanizingand coatings - electroplating. By the way, anodizing also relates to galvanothermy.

First learn to put on the steel surface copper. Chrome plating is very common in industry, and not only as a separate process, but also (perhaps even more) as a preparatory operation prior to coating other, more durable and elegant films - chrome, Nickel, silver. The reason is that copper, properly applied, is very firmly on the steel and smoothes roughness and surface defects, and other metals, in turn, is well deposited on the copper film. It would seem that everything is simple: treated steel part with a solution of copper sulphate, more active iron replaced the copper from the solution, and it settled on the surface. Indeed, it will be (you can check by lowering the net nail in a solution of CuSO4). But the copper layer on the surface is very loose - it's easy to erase cloth. And when the electrochemical machining of the copper layer is smooth and durable.

Here is a very simple method of copper plating. From one end of the soft stranded wire, remove the insulation and rasterbate thin copper wire to make a "brush". For convenience, tie her to a wooden stick or pencil, and the other end of the wires connect to the positive pole of the batteries for pocket lantern. The electrolyte is a concentrated solution of copper sulphate, preferably slightly acidic - pour into a wide bottle, which will be convenient to dip the brush tool.

Prepare a steel plate or other small item, preferably a flat surface. Wipe clean with fine emery cloth and degrease, boiling thoroughly in a solution of washing soda. Put the disc in the tray or cell and connect it by wire to the negative pole of the battery. The circuit is assembled, you only have to enter the electrolyte.

Dip the brush into the solution of copper sulphate and slide it along the plate, trying not to touch the surface; exercise so that between the plate and the brush was always a layer of electrolyte. Posting all the time should be moistened with a solution. In the eyes of the plate will be covered with a red layer of metallic copper. For processing small items will take a few minutes. If the surface is larger, it will require not only more time but also an additional battery, connect it in parallel with the first. When coated, dry the item in the air and a matte layer of copper RUB to Shine wool or woolen cloth.

By the way, this experience can be put and aluminum, and galvanized plate. This process, in which the part is immersed in the electrolytic bath, and treated outside of the small areas, adding the electrolyte, sometimes used in practice, especially in cases where the detail is so great that it cannot find a suitable bath. For example, when it is necessary to renew the coating on the hull of an ocean ship...

However, if the items are small, they usually still immersed in a bath of electrolyte is faster and more convenient. Here's how to do it when Nickel plating steel, or, more precisely, before plating, for without preliminary copper plating in this case is not enough.

A metallic object that you decided to cover the Nickel (let it be the water valve or plate for door), treat as usual, emery paper to remove the oxide film, wipe the brush, as it should rinse with water, degrease hot soda solution and rinse again. In a jar or glass lower on the tape (preferably copper) two copper plate anodes. Between them on the same wire hang the item (all these delays, remember, it's best to wrap around the pencil and put it on the edge of the banks). Those wires that go from the copper plates join together and connect to the positive pole of the current source, and the detail to the negative; switch in the circuit of the rheostat or radiocapacity 200-300 Ohms to regulate the current, and milliammeter (tester). The constant current source is two or three batteries for pocket lantern, connected in parallel, or a battery with a voltage of not more than 6 in.

The electrolyte solution 20 g of copper sulphate and 2-3 ml of sulfuric acid to 100 ml of water - pour into a glass, the solution should completely cover the electrodes. Using a rheostat or picking up resistance, set the current 10 to 15 mA per square centimeter of the surface details. Twenty minutes later turn off power and remove the item - it is covered with a thin layer of copper. The electrolyte copper plating pour, it will be useful.

Next is the actual plating. Prepare a new electrolyte (30 g of Nickel sulfate, 3.5 g of Nickel chloride and 3 g of boric acid per 100 ml of water) and pour the electrolyte into another Cup. For Nickel plating the desired Nickel electrodes. Dip them in the electrolyte, assemble the circuit as well as with madnani, and turn on the current, again for about twenty minutes. Remove the item, rinse and dry it. It is covered with a grayish matte Nickel. To cover acquired the usual Shine, it must be polished.

The electrolyte for plating usually contains chromic acid. But since this acid you have, probably not, will have to resort to a roundabout maneuver.

You have already received green chrome pigment. If you didn't put the experience, keep in mind that chrome green is sold in stores. Alloy chromium oxide with soda in the air, i.e., heat the mixture in a clean metal Bank. You got chromate sodium Na2CrO4. Dissolve it in water, strain and pocketlite sulfuric acid; this solution it is possible to carry out plating. Of course, if you have a ready chromate sodium, to cook it too.

A small object that you are going to chrome-plate, process as usual sandpaper, degrease, etch a weak acid solution and rinse. He will be the cathode, connect it to the negative pole of the current source. The anode of the desired inert, for example, graphite. Remove the old battery and remove the graphite rod.

To get a current, sufficient for chrome, you need to take the battery or multiple batteries for pocket lantern. Time and experience required current pick up yourself. At the end of the electrolysis remove the item from the electrolyte, wash it and Polish it to a Shine cloth and tooth powder.

O. Holguín. "Experiments without explosions"
M., "Chemistry", 1986

 

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