Corrosion Control of Stainless Steels in Indoor Atmospheres—Practical Experience (Part 2)

A survey of the ionic species deposited on surfaces over periods up to 20 years was performed in facilities constructed to store stainless steel containers for radioactive waste or facilities broadly representative of them. In the latter case, together with measurements able to yield direct information of aerosol deposition rates, a monitoring program aimed at characterizing temperature and relative humidity and evaluating corrosion phenomena on a prototype container (304L) over a period of about 10 years was established. The results show that ionic species such as chloride, sulfate, nitrate, carbonates, calcium, and sodium are predominant in the environment. Deposition rates on the order of 1 μg cm⁻²/y⁻¹ have been inferred for these species, while much lower levels and rates were found for magnesium and potassium. Compared with data on outdoor deposition and with seawater ionic ratios, these data indicate that contamination indoors is likely to be strongly affected by autogenous sources (e.g., concrete dust). The results of the monitoring program confirmed that very limited corrosion damage is observed on 304L/316L in natural conditions up to periods of about 10 years (deposition density ~10 μg cm⁻²) and that, upon exposure to higher contamination (~100 μg cm⁻²), a higher degree of corrosion but no stress corrosion cracking is found.