Heat-induced morphology-dependent corrosion of solid boric acid on carbon steel

The corrosion of solid boric acid (s-BA) has so far remained unnoticed, which could pose a potential hazard to the safety of boron-containing equipment. In this work, a morphology-dependent corrosion behavior of s-BA was found on Q235 carbon steel encompassing temperatures from 160 °C to 240 °C. Concurrent with the corrosion process, s-BA underwent a heat-induced morphology-transition from block-like into sheet-like/flake-like under the delayed decomposition condition, which emerged as a key contributor to the heightened corrosion rates after reducing the volume of the corrosion system. Through integration with the ex-situ pretreatment experiment, our analysis concludes that this morphology-transition accelerated corrosion by facilitating the generation of more Fe5O5[B6O10(OH)3] ·nH2O and filamentous amorphous corrosion products than FeB12O19·5H2O. The crucial relationship between s-BA with distinct morphologies and different types of borate products was also further expounded.