Burial environment and corrosion of socketed iron axe excavated from Yoshida Nakamichi site in Tottori City, Tottori Prefecture

Mitsui, Seiichiro

Koeki Zaidan Hojin Tottoriken Kyoiku Bunka Zaidanhen 2014 "Yoshida Nakamichi Iseki" Tottoriken Kyoiku Iinkai, p.221 - 230, 2015/03

http://kyo-bun.sakura.ne.jp/houkokusho/2015yoshidanakamichi.pdf#page=229

An ancient socketed iron axe was excavated from Yoshida Nakamichi site in Tottori City, Tottori Prefecture. To understand reasons of corrosion state of the axe, we studied relationship between burial environment and corrosion. As environmental conditions, we investigated groundwater chemistry and corrosion rate with iron probe monitor, etc. As for corrosion state, we analysed corrosion depths with a X-ray CT and corrosion products with a portable XRD/XRF. As results, we found that the redox potential and dissolved oxygen level as environmental conditions were very low, and that the maximum corrosion rate (210 mm/y) evaluated from measured corrosion depths was smaller than the probe corrosion rate (510 mm/y) by two orders of magnitude and identified siderite (FeCO) as a corrosion product. The results suggested that the siderite precipitated on the surface of the iron sword inhibited corrosion reaction.