Characterization of oxides of stainless steel UNS S30400 formed in offshore environment

Thick corrosion products of austenitic stainless steel obtained from a steam turbine structure exposed in offshore environment were studied by optical stereomicroscopy, X-ray diffraction, Mössbauer and energy-dispersive X-ray spectroscopy. The external surface of mechanical structure was exposed to a marine atmosphere and the internal one to a combustion gas for two decades. Characterization of corrosion products showed high content of akaganeite in the outer region and a mixture of akaganeite and hematite in the inner surface. Besides these characteristics, a distribution of nanosized superparamagnetic particles of akaganeite was found in the rusts.

► Thick corrosion products of stainless steel were characterized by Mössbauer spectroscopy.
► High content of akaganeite on the surface exposed to marine environment.
► Nanoparticles of akaganeite were always observed.