Evaluation of the applicability of dose–response functions incorporating time of wetness: Analysis of outdoor exposure test data for carbon steel and zinc across multiple countries

A dose–response function (DRF) incorporating time of wetness (TOW) as an input parameter was proposed by Ohara et al. (2024) based on outdoor exposure test data for carbon steel and zinc in Japan. The environmental input factors of the DRF include chloride deposition (S_d), time of wetness, and temperature. Corrosion rate maps were also generated by combining the proposed DRF with spatial distributions of these environmental factors. By expressing the S_d term in the DRF as an exponential function, the estimated corrosion rate maps successfully reproduced the decreasing trend with increasing distance from the coastline, indicating that the DRF is applicable to the evaluation of atmospheric corrosivity in Japan. In this study, the TOW-based dose–response functions proposed by Ohara et al. (2024) were examined with respect to their applicability to outdoor exposure test data for carbon steel and zinc obtained in multiple countries, including data from the ISOCORRAG program (Knotkova et al., 2010). Based on environmental data available in the ISOCORRAG database, the corrosion rates of carbon steel and zinc were estimated using TOW and S_d as input parameters. For data with S_d exceeding 200 mg m⁻² day⁻¹, primarily from coastal sites in Sweden, Norway and France, the corrosion rates were significantly overestimated. In contrast, for Sd below 200 mg m⁻² day⁻¹, the estimated corrosion rates showed better agreement with the measured values. These results indicate that the proposed TOW-based dose–response functions still face challenges in evaluating atmospheric corrosivity across multiple countries, particularly in regions with substantially higher chloride deposition.