Accession Number : ADA320572

Title :   Part I. The Effect of Dissolved Ozone on the Corrosion Behavior of Stainless Steels in Artificial Seawater. Part II. The Effect of Dissolved Ozone on the Corrosion Behavior of Ni-Cr-Mo Alloys in Artificial Seawater.

Descriptive Note : Rept. no. 3,

Corporate Author : RENSSELAER POLYTECHNIC INST TROY NY

Personal Author(s) : Wyllie, W. E., II ; Duquette, D. J. ; Brown, B. E.

PDF Url : ADA320572

Report Date : JAN 1997

Pagination or Media Count : 62

Abstract : The corrosion resistance of austenitic stainless steels in artificial seawater containing 0.2 to 0.4 mg/L dissolved ozone was investigated. According to cyclic polarization data, UNS S30400 and S31600 stainless steels are resistant to pit initiation after 8 weeks exposure to ozonated artificial seawater. However, if crevices exist, crevice corrosion is more severe in ozonated vs. aerated artificial seawater. Maximum crevice corrosion penetration rates of 8 and 5 mm/y were recorded for UNS S30400 and S31600, respectively, in ozonated artificial seawater compared to only 0.4 to 0.5 mm/y under aerated conditions. Mixed potential analysis of anodic and cathodic polarization predicts crevice corrosion rates for UNS S31600 that are in excellent agreement with the immersion sample data. Highly alloyed Ni, Cr, Mo, and N-bearing austenitic stainless steels are resistant to crevice corrosion in aerated and ozonated artificial seawater. However, differential oxidation corrosion was observed between surfaces of high and low ozone concentration, leading to local transpassive dissolution manifested as surface etching and superficial intergranular corrosion. After 47 weeks exposure to ozonated artificial seawater, microscopic pitting was observed in crevices of high alloyed stainless steels. Although intergranular corrosion and microscopic pitting of highly alloyed stainless steels are not considered severe, these modes of corrosion warrant further investigation in the interest of corrosion resistance in long term (> 1 year) service under oxidizing conditions in seawater.

Descriptors :   *STAINLESS STEEL, *CORROSION RESISTANCE, *NICKEL ALLOYS, *SEA WATER, *OZONE, *DISSOLVING, POLARIZATION, CRACKS, ETCHING, CYCLES, AUSTENITE, MICROSCOPY, SURFACES, CATHODES, OXIDATION, MIXING, IMMERSION, MOLYBDENUM ALLOYS, AERATION, PITTING, CHROMIUM ALLOYS.

Subject Categories : Inorganic Chemistry
      Properties of Metals and Alloys
      Physical Chemistry
      Physical and Dynamic Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE