In ancient times, people used ⊙ to represent gold and Э to represent silver, because gold always shines with the golden light of the sun, and silver always shines with the silvery white light of the moon.

Gold and silver usually do not rust, mainly because their chemical properties are too inactive, and they hardly combine with other elements. Even if heated to above 1000°C, they still refuse to combine with oxygen. The so-called real gold is not afraid of fire, which means that gold will not undergo chemical changes under high temperature.

Because of this, gold mines are pure gold in nature, and many silver mines are pure silver. So far, the largest natural gold nugget that people have found has a mass of 112 kilograms, and the natural silver nugget that people have found is 13.5 tons! And other metals, almost all exist in the form of compounds: iron ore-iron oxide, sphalerite - Zinc sulfide, bauxite-alumina, cassiterite-tin dioxide, galena-lead sulfide

However, gold and silver are not absolutely immune to rust. In aqua regia, gold corrodes. Aqua regia is the strongest acid and is a mixture of 1 part nitric acid and 3 parts hydrochloric acid (by volume). It can chemically react with gold to turn gold into a soluble compound.

Silver is more active than gold, not only aqua regia can rust it, but sulfur can also rust it and turn it into black silver sulfide. Bright silverware will turn black when rubbed with sulfur powder. Because of this, the surface of ancient silverware is often black, while ancient goldware is still shining. If you scrub silverware with ammonia, the blackened surface will quickly brighten and look new. This is because silver sulfide reacts with ammonia water and becomes a silver ammonia complex that is easily soluble in water. In the same way, the blackened copper can also be polished with ammonia water. Therefore, some people call ammonia water to wipe copper water.

Iron is a metal that rusts easily. Almost none of the ancient ironware displayed in the museum is not rusted; the kitchen knife will be covered with rust if it is not used for a few months. Every year, tens of millions of tons of steel in the world turn into rust.

Iron is easy to rust, in addition to its active chemical properties, it is also closely related to external conditions. Moisture is one of the conditions that makes iron rust. Chemists have proved that iron will not rust for several years in absolutely anhydrous air. However, water alone will not cause iron to rust. If a piece of iron is placed in a boiled, airtight bottle of distilled water, the iron will not rust. It turns out that only when oxygen and water act at the same time will iron rust. In addition, carbon dioxide in the air dissolves in water, which can also cause iron to rust. The composition of rust is very complex, mainly iron oxide, iron hydroxide and basic iron carbonate.

Rust is loose and soft, like a sponge. When a piece of iron is completely rusted, its volume can expand eight times. Spongy rust is particularly easy to absorb moisture, which makes the iron rot faster.

There are also many factors that make iron easy to rust, such as salt in water, unclean and rough surface of iron products, and impurities such as carbon in iron.

People have come up with all kinds of ways to protect steel. The most common rust prevention method is to put "clothes" on the iron—paint the surface of the iron or coat it with other metals that are not easy to rust. For example, the sedans were dressed in shiny spray paint; the heating pipes were painted aluminum; the tinplate used for the cans was tinned; the tin was coated with zinc.

A more thorough approach is to inject iron into a "strengthen needle" - adding other metals to make a stainless alloy. The famous stainless steel is an alloy made by adding a little nickel and chromium to the steel.

Star Harvest Jewelry, started in Dongguan, China, 2005, as a manufacturer specialized in production of 925 silver jewelry and quality brass jewelry. We concentrate on research, design, production of jewels.We have been providing OEM/ODM service for 17 years, helping our customers grow their brands and business.