Why is the sword unearthed by Gou Jian, King of Yue, still sharp after thousands of years?

Metal utensils in people's lives often rust. As the saying goes, "A sharp knife needs no yellow rust", but Gou Jian's sword is still as sharp as ever after more than two thousand years. According to Kao Gong Ji's records, craftsmen in the Warring States period have accumulated enough experience and mastered the technology of smelting bronze. The ratio of copper to lead and tin in the alloy is also different according to the purpose of the vessel. This smelting technology is ahead of western countries for nearly a thousand years.

The main components of Gou Jian's sword are copper, tin and a small amount of bronze alloy composed of aluminum, iron, nickel and sulfur. The sword body is vulcanized with black diamond pattern, and the precision grinding technology of the sword body can be compared with the products produced by modern precision grinder. Because different parts of the sword have different functions, the ratio of copper to tin is also different. The ridge of the sword contains more copper, which makes the sword tough and not easy to break; However, the bronze alloy of Gou Jian Jian's sword of Yue King has high tin content and high hardness, which makes the sword very sharp. The sulfur content in the pattern is high, and copper sulfide can prevent corrosion and keep the pattern gorgeous.

After testing, the researchers found that there was a layer of chromium salt compound with a thickness of 10 micron on the surface of Gou Jian's sword. This discovery immediately caused a sensation in the world, because this chromium salt oxidation treatment method is only a modern advanced technology. Germany invented and applied for a patent in 1937, and the United States in 1950.

The eternal stainless of the sword of Gou Jian, the king of Yue, is closely related to its preservation method besides its exquisite craftsmanship. 1983 Wu Wang fu cha spear with similar age and manufacturing process as Gou Jian's sword was unearthed from Mashan Chu tomb in Jiangling. However, due to the poor preservation of the tomb, most coffins have rotted. When the fork spear was unearthed, not only the handle was almost rotten, but also the bronze surface was covered with green rust.