How is it that the weapons of the world-famous Terracotta structures have survived for over 2,000 years? A new study now sheds light into what has really made the ancient weapons stand the test of time.

Terracotta Army

The Terracotta Army of Xi’an comprises of thousands of life-sized warrior figures within pits in the mausoleum of the first emperor of a unified China, Qin Shihuang. The warriors are equipped with weapons such as arrows, swords, and crossbow triggers, presumably so they would be able to protect the late emperor even in the afterlife. While many of the weapons had already deteriorated in the past 2,000 years, the bronze weapons have remained in pristine condition.

Since the Terracota Army was discovered in the 1970’s, researchers have surmised that the reason behind the bronze weapons’ remarkable condition is that it was likely a result of an ancient anti-rust method that the makers of the weapons developed. Supporting this hypothesis are the traces of chromium on the weapons, suggesting that they used a kind of chromate conversion coating technology, something that was patented in the 20th century and is still being used today.

However, researchers of a new study found that not all of the best preserved weapons had traces of chromium in them. So what does this mean for the theory?

Bronze Weapon Preservation

To investigate the possible reasons for the weapons’ excellent preservation, researchers tested weathering of replica bronze weapons in environmental chambers. In one, the replica was buried in Xi’an soil, and in the other, the replica was buried in British soil. Interestingly, after four months in the chambers, the replica weapon buried in British soil had severe corrosion, while the one buried in Xi’an soil was still in pristine condition.

As such, the researchers believe that the excellent preservation of the bronze weapons were due to the soil conditions in the surrounding area, than an ancient anti-rust technology. Furthermore, it is possible that the chromium traces on some of the weapons were for decorative purposes, and not for preservation.

The study is published in Scientific Reports.