Good afternoon! In this article, we will consider the process of electrochemical deposition of copper on conductive surfaces, and also try to cover the walnut with a copper layer.
So, for the experiment we need:
Non-metallic container - chemical beaker or conventional tray, the precipitation process will take place;
Water, preferably purified;
Copper sulfate ( sold in stores to give);
Acid electrolyte for batteries (in auto shops);
Charger 5 Volt, 0.3 Ampere;
1 kΩ and 220 ohm resistors to limit the applied current;
Try on metal
Fall asleep in capacity 100 sulphate, fill half a liter of water and add 70 grams of acid electrolyte.
Mix and filter through a funnel and cotton pad. Install and fix the copper electrode:
Plus power from charging will be connected to it. We make three drops from the minus: we solder the resistor by 1 kΩ to the first, and by 220 ohms to the second.
This way we can comfortably control the supplied current. When the charger is turned on, a chemical process called electroplating will start. Under the influence of electric current, copper atoms on the positive contact are oxidized and dissolved in the electrolyte, then settle on the negative. The current of the power source is selected at the rate of 1 Ampere per 100 cm² of the surface to be coated.
First, let us cover the usual iron nail with copper. Coverage area - 10 cm². We clean with sandpaper:
We connect to the power supply minus through a 1 kΩ resistor, and lower it into the solution. After 30 seconds we get and wipe with a cotton disc.As a result, the layer turned out quite loose and erased.
Now let's try to create a truly resistant coating. To do this, clean the nail and connect it through a 220 ohm resistor, lower it into the solution for 10-15 seconds. Then change the resistance by 1 kΩ and leave for half an hour. That's what happened:
This time the coating turned out to be durable and did not leave any traces on the disk at all. After sandpaper, a small part of the copper still covered the nail. Try to cover the lead cake with copper. If you connect it through resistance, even after a few minutes, the result will be insignificant.
But it is necessary to connect directly, as after a minute the cake is completely covered with copper.
If the area of the cover is too small,then you can see a darkening on it:
This phenomenon is called soot and is due to the fact that too much current flows through this surface.
We cover the copper nut
We understood with metals, but what about dielectrics, they do not conduct current and the reaction simply does not begin. But there is a solution: you need to cover our subject with conductive material. The last one is fine graphite, from which rods are made for simple pencils.
Take the softest pencil. Soft pencils are marked with the letter “B”, and the number at the beginning indicates the degree of softness. A fine pencil handles fine detail better. We color our nut.
The application of graphite in this way is a very tedious task, therefore in building stores a special graphite spray is sold.He will cope with this task much faster. After coloring with a drill, manually make a hole under the “twig”. We pour super glue into it, cork it with thick copper wire and fall asleep with graphite powder remaining after decorating the nut.
Connect the minus of the power to the wire through a 1 kΩ resistor. At this stage, you should not apply a large current, otherwise the copper layer will turn out loose, which is not good. Half an hour later, the nut was covered with copper a little and you can reduce the resistance to 220 Ohms.
Even after some time, the growth of copper will slow down and you will have to reduce resistance. To do this, we use the tree block and nichrome thread, strung on a screw snake at its edges.
We set the resistance to 70 Ohms. When the copper covers the nut completely, set the value of the improvised resistor to 5 Ohms and leave the nut for another five hoursfor thick and uniform coverage. During this time, the copper electrode has been greatly depleted.
All this copper has settled on our nut, creating a rough layer.
At the end of the process, the nut noticeably gained weight.
In order to bring a pleasant shine to the copper surface, we will cover it patina, and then we polish. For this we need:
Ammonia, also ammonia solution;
Sulfuric checker (can be found in stores to give);
Chemical or disposable glass;
Fine-grained emery paper.
Pour into glass a little ammonia and crumb a little sulfur. We drop a nut there, as shown in the photo.
The glass must be covered with something, because hydrogen sulphide is released during the reaction - a gas with a strong odor. After 20 minutes, the nut is very dark, take it out of the glass.Bite off the “twig”, end up with the pliers in the eyelet.