Rhodium. Properties and uses of rhodium

Rhodium plating of gold jewelry is the application of a thin layer of rhodium to the surface of the metal. This allows the product to acquire a special shine, improve its original quality and characteristics, which will help to be more resistant to external irritants. The metal itself has a special light shade and metallic luster, which, at first glance, is very similar to silver. The use of rhodium-plated coating has become relevant because the material is resistant to corrosion and has high strength. Jewelers who deal with rhodium plating gold are ready to tell you what it is in this article.

What is rhodium plating used for?

Rhodium plating of gold or other metal will mean applying a layer up to 25 microns thick to the surface of the jewelry. This helps products acquire a number of advantages that they did not have before, namely:

1. Increased strength.
2. Lack of perception to external stimuli.
3. Hypoallergenic.
4. Shine.
5. No darkening over time.
6. Original appearance.
7. Resistance to reagents.
8. Corrosion resistance.
9. Resistance to non-standard temperatures.

Why rhodium?

Rhodium is a platinum group metal. Its advantages over other types are high hardness, original light and resistance to corrosive environments. And the high cost is explained by its rarity - only about 3 tons are mined per year.

Most white gold jewelry is plated with rhodium, otherwise it would not have such a shine, since without rhodium plating, Au has a duller color. Such a coating is capable of reflecting 80% of the light that hits it, while gold in its normal state can only reflect 65%, even if it is perfectly polished.

Rhodium on gold favorably sets off the precious stones on the jewelry, so a layer of metal is often applied separately in place of any inserts.

Together, all these advantages made metal the main one for giving jewelry its original appearance and protecting it from various types of irritants. Rhodium has properties that other metals of the platinum system cannot boast of.

Is rhodium dangerous for humans?

This metal was discovered by the English scientist William Hyde Wollaston during scientific research in 1803. Its name is translated from Greek as rose. The substance has a refined white color with a grayish-bluish tint. It belongs to the precious metals of the platinum group.

Rhodium has unique properties, namely that it has very high corrosion properties (this indicator is twice that of platinum), and quite high hardness, in which it is only slightly inferior to iron.

But why don’t they make jewelry out of it, but only spray it on it? The point here is that Rhodium is a rather fragile material and there is nothing surprising here; it is often enough to remember diamond, which is the hardest mineral, but it can be easily broken.

What qualities have turned it into the number one material for coating products:

— High strength, resulting in no scratches

— High corrosion resistance, due to which the coating does not darken over time

— Beautiful unusual color

- Hypoallergenic properties, it does not cause allergies

After we have examined the basic properties of this metal, we can answer the question posed at the beginning of the article whether rhodium is dangerous for humans or not. The answer is clear no, and on the contrary, it is very useful because, unlike other metals, it does not cause allergies and does not react with the skin.

Rhodium is very rare in nature and therefore very expensive. Let me give you an example of this fact: from eight kilograms of platinum, 1 kg of Rhodium is obtained. Its main deposits are located in Mexico 48%, and South Africa 23%. Not so long ago, the price for it was around $10,000 per troy ounce, but due to the economic crisis in the automotive industry, the price dropped to $900. Less than 30 tons of this material are mined per year worldwide.

Nowadays, this material has found wide application in jewelry. It is used for:

— Coatings

— Platinum alloying

— For protection against oxidation.

The following metals are subjected to rhodium plating: 1) White and red gold, 2) Platinum, 3) Silver, 4) Steel parts of watch movements of famous brands.

The influence of Rhodium on the modern jewelry industry can hardly be overestimated, thanks to this magnificent coating that protects the surface of jewelry from corrosion, oxidation and, most importantly, scratches, craftsmen manage to create real masterpieces of jewelry that will delight more than one generation of people.

You can order Slavic amulets, amulets, talismans coated with Rhodium in the online workshop Your Slavic Master ().

How does rhodium plating occur?

What is rhodium plating and how does it happen? First, a specialist must prepare the surface of the product. He carries out preliminary polishing or grinding, this is necessary in order to obtain a perfectly clean and smooth surface for adequate application of rhodium plating. This procedure is typical for those jewelry that did not undergo rhodium plating immediately after manufacture.

Then the finished product must be degreased and washed to proceed to the last stage, lowering it into a galvanic bath containing a special solution. An electric current passed through this solution promotes the release of rhodium, which in turn begins to coat the gold with a thin layer.

The solution acts as a conductor for the metal salts that will be deposited on the surface of the gold. Among themselves, experts call this process “cooking.” The liquid has a negative charge, and the molecules of the deposited elements have a positive charge. This happens so that when current passes through the liquid, the negative begins to be attracted to the positive. And as a result, this workpiece is coated with rhodium.

To perform rhodium plating on jewelry, it is worth preparing water-soluble salts of the valuable metal, but obtaining them is not so easy.

It will also require complex installation parts. Therefore, enterprising people began to produce a ready-made composition of rhodium sulfate. After this, you can simply dilute it with water and obtain the required electrolyte.

It is not for nothing that the thickness of the rhodium plating is set at 25 microns. With a greater thickness of the layer from the inside, rhodium may tend to internal pressure. In this case, microcracks or pores may form. If this happens, gold rhodium plating will be useless.

Chemical substance rhodium

The simple chemical rhodium is a hard transition metal that is silvery-white in color. Rhodium belongs to the noble metals of the platinum group.

It is important! Among all the unique properties of rhodium, it is worth noting that in terms of resistance in most corrosive environments it is significantly superior to platinum.

In general, the main chemical properties of rhodium are:

• the possibility of dissolving the metal when boiling in aqua regia, which is a mixture of two acids: nitric and hydrochloric;
• the ability to dissolve in hydrogen peroxide and sulfuric acid;
• this metal has high chemical resistance;
• rhodium reacts with non-metals only at red heat;
• The oxidation process of rhodium occurs at temperatures above 600 degrees Celsius.

Rhodium is a unique precious metal , the scope of which is diverse.

Rhodium is often used in catalysts , in particular, in catalytic filters, which are catalysts for automobile exhaust gases.

An alloy of rhodium with its “brother” platinum is a very effective catalyst in the production of nitric acid by oxidizing ammonia with air. It is in this area that rhodium as a catalyst metal has no analogues.

Rhodium plating of gold jewelry

Rhodium plating of gold jewelry is most common. Such statistics are tracked because the price of gold jewelry is higher than that of other metals, so the owners of these particular rings and other types of products want to preserve their elegant appearance for as long as possible.

There are several goals that people pursue when giving gold for rhodium plating, these are:

1. Covering the fastener area.
2. To highlight the color of the stones.
3. Devotion to originality in decoration.

Sometimes clients only plan to attach the stone to jewelry, it could be a ring or earrings - in this case, a layer of rhodium is also applied to the place of the future stone, which will initially show the stone in the most favorable light.

Rhodium is applied to the clasp to strengthen it, ensuring its durability and protecting it from mechanical damage. If we talk about stones, a rhodium-plated diamond, as well as cubic zirconia, topaz or emerald, will look very advantageous.

The metal is often used to produce black gold. This decoration increases its price due to its durability and spectacular appearance. Precious stones look especially beautiful against the background of such gold.

Sometimes rhodium can be crossed with titanium - this combination will give the color of the product an original pearlescent tint; They can also add a little silver to the composition.

Rhodium-plated white gold also commands a high price. But this does not reduce the huge demand for such jewelry.

Properties of rhodium

Why has rhodium become widespread in jewelry? The metal owes its popularity to its unique properties, which are superior to those of other precious metals. For example, the melting point of rhodium is 1964 degrees, which is exactly 900 higher than that of gold, and 1003 higher than that of silver.

In addition, rhodium coating gives the products additional strength and wear resistance, because the hardness of this metal on the Mohs scale is determined by six units, while other popular metals have an indicator of only 2.5. The durability of the coating is also determined by the high resistance of rhodium to chemicals. Oxidation processes begin in the metal only when heated above 600 degrees.

The visible positive characteristics of the material include a beautiful cold shine, which remains unchanged for many years.

Why is such noble, durable and beautiful rhodium not used as a base in jewelry? The fact is that the metal is very fragile, and without an additional base of another material it can quickly crack. This is observed even during the repair of some products coated with rhodium, when its layer breaks off in parts and then requires reapplication.

Rhodium plating of red gold

Rhodium plating of red gold, what is it? The process is absolutely no different from applying a layer to white or yellow gold. The properties will also be similar, what is the difference then? In fact, red gold is not rhodium-plated as often as jewelry, when compared with other types. There are several reasons for this.

Firstly, the price of such jewelry is more likely to fall than rise, since there will always be problems with the rhodium layer being erased, after which these gaps will be visible at first glance. As you know, the price of rhodium plating is not so low, and in this case re-application will be required quite often.

To partially solve the problem, rhodium is not completely applied to the product, but is applied to places where stones are installed, and there is a minimal likelihood that the layer will be erased.

How to care for rhodium-plated gold?

Once it has become clear what rhodium plating and rhodium plating in general are, the question of caring for such jewelry becomes relevant.

To begin with, you should understand that if a product has a rhodium coating, this does not mean that it will last forever, so you need to take care of it initially and remove it as soon as there is no longer a need to wear such jewelry. After all, if the layer begins to wear off, the product will take on a very unpleasant appearance.

There is no special technology for caring for rhodium-plated gold. You just have to follow a few simple rules for storing these jewelry, these include:

• storing gold in a separate box, and not where other jewelry is kept;
• do not allow unnecessary access to reagents;
• if you plan to wash dishes, it is better to remove the rings;
• Don't forget to take off your jewelry before going to bed.

But if it was not possible to save the jewelry or simply took its toll, repeated rhodium plating can be done in almost any specialized workshop.

The service will cost from 800 to 2000 rubles, depending on the product and its complexity.

Price table for rhodium plating of jewelry made from different precious metals: