What is gold plated brass? Electroplating, gold plating of copper, brass, gilding. Recycling leftover gold from dirty or depleted baths

Today we will talk about how to do your own gilding, gilding, gilding or silvering, and silvering various metal surfaces at home. Do-it-yourself chemical and galvanic methods and technologies for silvering and gilding metals

Gilding products made of steel, copper and other metals and alloys is not an easy task! Here, both in preparing reagents and in preparing products for gilding, experience is required. The slightest inaccuracy in technology, a tiny mistake in a recipe can negate not only the results of the work, but also irreversibly destroy the precious metal.

Therefore, to gain experience, and just to be on the safe side, first comprehend all upcoming operations and manipulate first with small quantities of reagents. Do not throw away spoiled solutions, but collect them in separate containers for their possible regeneration, as well as the release of gold.

It is known that gold gives good adhesion to bases made of copper, brass and silver. But alloys containing nickel (for example, stainless steel) require special preparation, therefore, when gilding nickel products, an underlayer of copper is usually applied to their surface.

There are both galvanic and chemical methods of gilding. But electroplating at home is very difficult, since this process will require special equipment (galvanic bath; a source that allows you to provide a current density of 0.1-0.3 A/dm2, a system for heating the electrolyte to 70-80 ° C), and There are also quite rare reagents - expensive and poisonous, which are usually not available for public sale.

Chemical gilding methods are much more practical. True, compositions for chemical gilding also include cyanide compounds, but not based on poisonous potassium cyanide, but on the basis of harmless yellow blood salt.

The basis of all recipes for chemical gilding is gold cyanide. To prepare it, you will need to make “aqua regia,” that is, a mixture of concentrated acids: hydrochloric acid HCl and nitric acid HNO3, taken in a ratio of 3: 1 (by volume). We prepare "royal vodka" in a porcelain vessel. Remember, this operation is very dangerous! Protect your eyes, skin and respiratory system. Mixing acids must be carried out under a hood or, in extreme cases, in the open air. The finished “royal vodka” is kept covered for a day.

Next, we prepare the gold: we forge the gold object into foil and cut it into pieces. We load these pieces into “aqua regia” at the rate of 1 g of gold per 10 ml of solution and wait for them to dissolve (this can take 2-3 hours or 2-3 days - it all depends on the strength of the acids and the thickness of the pieces of foil). The resulting solution is drained from the sediment.

We collect a water bath and carefully evaporate the solution at 70-80 ° C, stirring it with a glass rod, until a thick, dark yellow “syrup” is obtained. The solution must not be overheated, as the gold will form an insoluble precipitate. The resulting “syrup” containing AuC13 gold chloride will be used as the basis for compositions for the upcoming gilding.

Now let's deal with the actual solution for chemical gilding. In a porcelain cup with a capacity of 2-3 liters (a 3-liter glass bottle, thoroughly washed, of course, is also suitable) a mixture of 2 liters of hot (50-60°C) distilled water (or “coat” water from the refrigerator freezer), 15 g syrup (gold chloride), 65 g potash (potassium carbonate K2CO3), 65 g table salt ("Extra"). We carefully clean the object intended for gilding from fat by boiling it in washing soda or in a 10-20% NaOH solution, and after washing we pickle it in 25% hydrochloric acid, after which we wash it again.

All that remains is to pour the required amount of hot (50-60°C) solution for gilding into a porcelain container, immerse our product in the solution and touch it with a zinc stick. A layer of gold appears on the surface of the product. We remove the product, wash it and lightly polish it with a woolen cloth.

There is also a simpler method of gilding - by rubbing, but the applied layer of gold is thinner.

Rubbing paste:

gold chloride…………….10 g
yellow blood salt......30 g
cream of tartar (creamortartar, KS4N5O6)...5 g
ground chalk (tooth powder)…………….55 g

Add water to the mixture of components until a slurry forms, and with a woolen cloth rub this slurry over the product, previously degreased, pickled with hydrochloric acid and washed in water.

If the gold plating turns out to be uneven and spotty, preliminary copper plating of the product will help.

A practical method for electroless copper plating of iron and steel is as follows. First, the product is coated with a brush with a solution consisting of 20 g of hydrochloric acid, 20 g of water, 10 g of zinc chloride. Allow the solution to drain, after which a second composition is applied (with a different brush), prepared from 10 g of copper sulfate and 160 g of water.

When this solution is prepared, a precipitate forms, and in order to dissolve it, ammonia is added to the composition.

Less high-quality copper plating involves immersing a pre-pickled iron (steel) product in a solution containing 50 g of copper sulfate, 50 g of 98% concentrated sulfuric acid and 1 liter of water. Just remember that you need to pour the acid into the water.

Both copper plating and gold plating can be done at home, but success depends on meeting the following requirements:

Competent preparation of solutions;
use of pure reagents;
use only distilled water;
thorough preparation of the surface of products;
compliance with temperature conditions.

Therefore, before you decide to gild, carefully assess your capabilities, and only when you find them sufficient, get down to business.

Common names and formulas of the reagents used:

Potash - potassium carbonate K2CO3;
yellow blood salt, yellow blue-kali - potassium iron sulfide K4)