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posted by martyb on Friday April 05 2019, @02:32PM   Printer-friendly
from the a-down-to-earth-answer dept.

In a cooperative project, University College London and Terracotta Army Museum researchers have published a study in Scientific Reports that sheds light on a forty year old mystery of why Terracotta weapons have not degraded over time as would have been expected.

The thousands of fantastic life-sized warriors in the Terracotta Army of Xi'an were armed with fully functional spears, lances, hooks, bows and arrows.

While the organic portions of these weapons such as wooden shafts and scabbards have deteriorated with time, the bronze components are in far better condition than they should be.

This was originally thought to be due to an ancient anti-rust treatment that was akin to modern chromate conversion coating technology, but the researchers indicate chrome found was due to a lacquer not even applied to the weapons

The terracotta warriors and most organic materials of the mausoleum were coated with protective layers of lacquer before being painted with pigments - but interestingly, not the bronze weapons.

We found a substantial chromium content in the lacquer, but only a trace of chromium in the nearby pigments and soil - possibly contamination. The highest traces of chromium found on bronzes are always on weapon parts directly associated to now-decayed organic elements, such as lance shafts and sword grips made of wood and bamboo, which would also have had a lacquer coating. Clearly, the lacquer is the unintended source of the chromium on the bronzes - and not an ancient anti-rust treatment.

The local soil composition, high-tin content of the bronze, and quenching technique were cited as contributing factors in the weapons' remarkable preservation.

Bronzes buried in Xi'an soil remained almost pristine after four months of extreme temperature and humidity, in contrast to the severe corrosion of the bronzes buried for comparison in British soil.

The researchers note that although their research largely explains the mysterious longevity of the weapons, there may still be a mysterious Qin Dynasty weapon preservation process in play as well, so further investigation is warranted.

Surface chromium on Terracotta Army bronze weapons is neither an ancient anti-rust treatment nor the reason for their good preservation (open, DOI: 10.1038/s41598-019-40613-7) (DX)


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  • (Score: 0) by Anonymous Coward on Friday April 05 2019, @09:37PM

    by Anonymous Coward on Friday April 05 2019, @09:37PM (#825136)

    "Made in Japan" and "Made in Korea" are the goods to get. "Made in China" is ... serviaceable, one step below, say, "Made in Vietnam".