The measurement of ultra low uniform corrosion rates

The safe long-term disposal of radioactive waste arising primarily from power generation is a complex proposition. Safety assessment modelling typically incorporates up to one million years, which is an engineering requirement without precedent. In order to perform this modelling, it is imperative that the behaviour of the materials comprising the repository are well understood over the timescales in question. This article describes a method developed for studying the behaviour of metals under anoxic conditions via the corrosion reaction end product, hydrogen. At its simplest, test cells are left for periods of time, up to several months, to accumulate hydrogen. This gas is then expelled from the cell and analysed using a hydrogen sensor. As such, the method is limited to characterising gas generation and consequently only uniform corrosion, but does permit direct monitoring of corrosion rates as low as 0.01 nm/year, which is necessary in order to accurately monitor the very low long-term corrosion rates expected in a deep geological repository.