The global performance envelope: Mapping climate extremes of water temperature and salinity for offshore wind turbine blade raindrop erosion

Rain erosion testing of wind turbine blade coatings is still based almost entirely on kinetic test parameters while ignoring the temperature–salinity domains that control field damage. This short communication quantifies how far current rain erosion test conditions diverge from offshore environmental temperature–salinity envelopes. Using seas surface climatology for four offshore regions (North Sea, US Atlantic shelf, Taiwan Strait–South China Sea, Bass Strait) and temperature and water composition parameters from 11 water-based erosion studies, we show the environmental sea surface temperature (SST) spans 5 – 17 °C in the North Sea and 8 – 24 °C in the US Atlantic, rising to 20 – 32 °C in the Asia–Pacific and Bass Strait, with sea surface salinity (SSS) typically 31 – 35.5 PSU. In contrast, all reported droplet erosion tests were run between 18 and 29 °C; three of 11 used only freshwater (~ 0 PSU) and the remainder a single seawater-like level (3.0 – 3.5% NaCl, ≈30 – 35 PSU). No study combined marine salinity with cold (<10 °C) or tropical (≥28 – 30 °C) temperatures, despite evidence of markedly higher damage in saline media and up to an order of magnitude increase in polyurethane rates near the glass transition region.