Eashwar, M. and Subramanian, G. and Palanichamy, S. and Rajagopal, G. and Madhu, S. and Kamaraj, P. (2009) Cathodic behaviour of stainless steel in coastal Indian seawater: Calcareous deposits overwhelm biofilms. Biofouling, 25 (3). pp. 191-201. ISSN 0892-7014

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Abstract

Type-316 stainless steel (SS) was investigated as the cathode in galvanic couples in full-strength seawater from the Gulf of Mannar on the southeast coast of India. Tests were devised to examine the impact of SS cathodes on anode materials with or without the accrual of marine biofilms. Biofilmed SS cathodes significantly enhanced the rate of corrosion of nickel, causing noble shifts in the couple potentials. With mild steel and zinc as the anodes, calcareous deposits developed quite rapidly on the SS cathodes and led to a significant reduction of bacterial numbers. The calcareous deposits also caused substantial reduction of galvanic corrosion rates for mild steel, whereas there was no difference for zinc. The deposits were identified by XRD as essentially carbonates, oxides and hydroxides of calcium and magnesium. Potentiodynamic polarization performed on the actual couples after disconnection and equilibration provided reasonable interpretations of the galvanic corrosion trends. Data from this work suggest that a potential of about 70.70 V vs. saturated calomel electrode (SCE) should provide optimum protection of SS in warmer, fullstrength seawater that supports the precipitation of calcareous deposits. The criterion commonly recommended for temperate conditions of lower water temperature and estuarine waters of lower alkalinity is 71.0 V (SCE).

Item Type:	Article
Uncontrolled Keywords:	stainless steel; seawater; biofilms; galvanic couples; cathodic protection; calcareous deposit; protective potential
Subjects:	Corrosion Science and Engineering
Divisions:	UNSPECIFIED
Depositing User:	TTBD CECRI
Date Deposited:	20 Jan 2012 14:14
Last Modified:	20 Jan 2012 14:14
URI:	http://cecri.csircentral.net/id/eprint/253

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