Hydrogen Absorption into Fe Plates with Rust Layers Containing Various MgCl2 Amounts during Atmospheric Corrosion with Controlled Humidity

• Published in: ISIJ International 2021/04/15, Vol.61(4), pp.1179-1185
• Main Authors: Haruna, Takumi, Wang, Yang, Yamanishi, Jun
• Format: Article
• Language: English
• Subjects: atmospheric corrosion; deliquescence; hydrogen absorption; hydrogen concentration in iron; hydrogen embrittlement; MgCl2 salt; relative humidity; rusted iron
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.ISIJINT-2020-502

Fe plates with rust layers containing various MgCl2 amount were prepared as specimens. Each specimen was subjected to dry/wet repeat test beyond 50 cycles, and then subjected to electrochemical hydrogen absorption test under atmospheric corrosion in the air with controlled relative humidity (RH). For an MgCl2 amount of 39.8 g·m−2, a hydrogen absorption rate (iH) started to increase from an RH around 15%, steeply increased with an increase in RH up to about 30%, steeply decreased up to about 35%, gradually increased up to 65% and gradually decreased up to about 92%. A decrease in MgCl2 amount in the range between 0.514 and 39.8 g·m−2 induced a decrease in iH in wide RH range. The maximum iH at an RH around 30% increased with an increase in MgCl2 amount in the rust layer. Besides, the RH where the maximum iH was obtained beyond an RH of 40% increased with a decrease in MgCl2 amount. From theoretical relationship between RH and thickness of MgCl2 solution film on the Fe plate without rust layer, it is found that the solution film thicknesses at the RHs were about 0.18 mm, almost independent of MgCl2 amount. In addition, thicknesses of the rust layers containing 25.7 and 39.8 g·m−2 MgCl2 were measured to be almost 0.18 mm each other. The trends of iH depending on MgCl2 amount were tried to be explained using nature of deliquescence for MgCl2.