Biofilm colonization dynamics and its influence on the corrosion resistance of austenitic UNS S31603 stainless steel exposed to Gulf of Mexico seawater.
Viable bacterial counts, chemical markers, phospholipid fatty acid analysis (PLFA), and Fourier-transformed infrared spectroscopy (FTIR), together with electrochemical methods, were used to study biofilm dynamics and its impact on the corrosion resistance of UNS S31603 stainless steels exposed to the Gulf of Mexico seawater. Biofilms progressively accumulated, peaking on day 20, but finally detached. The extracellular polysaccharide (EPS)/cellular biomass ratio remained low most of the time, but reached its highest level (4.2+/-1.9) also on day 20. Viable bacterial cells reached their highest abundance earlier (approximately 800 CFU/cm2), on day 15. Biofilms were seen covering the stainless steel surfaces heterogeneously and were composed mainly of gram-negative rods, presumably EPS-producing bacteria. Despite the different levels of biofilm biomass and attachment state, field-exposed steel coupons ennobled significantly and showed more active pitting potentials (approximately +500 mVSCE) than on the abiotic control (+650 mVSCE), where no significant ennoblement occurred. These results suggest that the heterogeneous distribution of biofilms, as opposed to the quantity of surface-associated biomass, promotes formation of differential aeration cells, and that this in turn contributes to the ennoblement of these steels.
Acuña
Narciso
N
Departamento de Materiales y Corrosión, Programa de Corrosión del Golfo de México, Universidad Autónoma de Campeche, Av. Agustín Melgar, C.P. 24030, Campeche, Campeche, Mexico.
Ortega-Morales
Benjamin Otto
BO
Valadez-González
Alex
A
D018441:Biofilms / Q000254:growth & development*; D018533:Biomass; D015169:Colony Count, Microbial / Q000379:methods; D003343:Corrosion; D017377:Diatoms / Q000648:ultrastructure; D004563:Electrochemistry; D016946:Gram-Negative Aerobic Rods and Cocci / Q000302:isolation & purification / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning / Q000379:methods; D011135:Polysaccharides, Bacterial / Q000032:analysis; D011157:Population Dynamics; D012623:Seawater / Q000032:analysis / Q000382:microbiology*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013193:Stainless Steel / Q000737:chemistry*; D013997:Time Factors; D014329:Tropical Climate
D011135:Polysaccharides, Bacterial; C426023:austenitic steel; D013193:Stainless Steel