Accession Number : ADA308266

Title :   Fundamental Studies on the Corrosion Behavior of Weldments in Marine Microbial Environments.

Descriptive Note : Final technical rept. 30 Sep 92-31 Jan 96,

Corporate Author : TENNESSEE UNIV KNOXVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Buchanan, R. A. ; Lundin, C. D. ; Angell, P. J. ; Danko, J. C. ; Kovacs, A. L.

PDF Url : ADA308266

Report Date : APR 1996

Pagination or Media Count : 84

Abstract : Weldments representative of a range of marine structural materials, in both creviced and non-creviced conditions, were exposed to a natural marine environment at a University of Delaware site on the Delaware Bay. Lewes, Delaware. Companion laboratory control tests were conducted at the University of Tennessee in 0.2 um filtered Delaware Bay water and in synthetic seawater. The weldments studied were: 304L, 31 6L and AL-6XN stainless steels; HY-80 and HSLA-80 low-alloy steels; Alloy 400 Ni-Cu alloy; 90-10 Cu-Ni alloy; 5086 aluminum alloy; and unalloyed titanium. Open-circuit potentials (OCPs) and corrosion rates were evaluated for all tests. In the non-creviced condition, ennoblement of the OCP, relative to the laboratory control tests, occurred for all weldments. Clearly, a microbial effect at the Delaware Bay site was responsible for this ennoblement. For the creviced condition, in most cases, the OCPs in the natural microbial environment were less than those in the laboratory control environments -- a result likely due to the higher crevice- corrosion rates in the natural microbial environment. With regard to corrosion rates, the microbial influence resulted in significant corrosion acceleration for the 304L, 31 6L, Alloy 400, and 90-10 Cu-Ni weldments, and moderate acceleration for the low-alloy steel weldments, HY-80 and HSLA-80. On the other hand, the microbial influence resulted in corrosion inhibition for the aluminum alloy and titanium weldments. For the AL-6XN weldments, the microbial influence produced corrosion inhibition in the non-creviced condition, but corrosion acceleration in the creviced condition. A microbially influenced corrosion (MIC) factor was defined and used to quantify the corrosion results. Based on results of this study, a new, simple, abiotic laboratory screening test for MIC was proposed.

Descriptors :   *ENVIRONMENTS, *CORROSION INHIBITION, *WELDMENTS, *MICROORGANISMS, CONTROL, LABORATORY TESTS, CORROSION, ALUMINUM ALLOYS, ACCELERATION, CRACKS, SITES, RATES, ALLOYS, STEEL, LOW LEVEL, LABORATORIES, TITANIUM, UNIVERSITIES, CIRCUITS, TENNESSEE, SEA WATER, OCEAN ENVIRONMENTS, CONSTRUCTION MATERIALS, ABIOTIC PROCESSES, DELAWARE, DELAWARE BAY.

Subject Categories : Microbiology
      Physical Chemistry
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE