title: The enrichment of surface passive film on stainless steel during biofilm development in coastal seawater.
abstract: The surface passive film on UNS S30400 alloy was characterized before and after biofilm development under different regimes of diurnal lighting in quiescent flowing coastal seawater. As exemplified by atomic force microscopy, the passive film grew under all test conditions with conspicuous variations in morphological features. X-ray photon spectroscopy illustrated an enrichment of the outer film by iron oxide and a progressive increase in the iron oxide/chromium oxide ratio with lighting. Mott-Schottky plots reflected the duplex nature of the film, comprising an outer n-type and an inner p-type configuration. The slopes of the plots showed a strong decrease in donor and acceptor densities with biofilm coverage and lighting, thus confirming passive film growth. These results provide new insights that passive film enrichment is an intrinsic process under practical marine conditions, and show that the evolution of the passive film is a key step to sustained passivity and/or its breakdown by microbial mechanisms.
authors.affiliation: a Corrosion Research Centre , CSIR - Central Electrochemical Research Institute , Mandapam Camp , Tamil Nadu , India.
authors.forename: M
authors.initials: M
authors.lastname: Eashwar
authors.forename: G
authors.initials: G
authors.lastname: Sreedhar
authors.forename: A
authors.initials: A
authors.lastname: Lakshman Kumar
authors.forename: R
authors.initials: R
authors.lastname: Hariharasuthan
authors.forename: J
authors.initials: J
authors.lastname: Kennedy
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D057219:Biofouling; D017608:Chromium Compounds / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry; D018625:Microscopy, Atomic Force; D056951:Photoelectron Spectroscopy; D012623:Seawater / Q000737:chemistry*; D013193:Stainless Steel / Q000737:chemistry*
chemical_list: D017608:Chromium Compounds; D005290:Ferric Compounds; D013193:Stainless Steel; C000499:ferric oxide; C023600:chromic oxide
keywords: marine biofilm; passive film; passivity breakdown; semiconductivity; stainless steel in seawater; sunlight; sustained passivity