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A model for prolonged dezincification of α‐brasses in 3% sodium chloride buffer solutions at different pH values
Author(s) -
Rehan H. H.,
AlMoubarak N. A.,
AlRafai H. A.
Publication year - 2001
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/1521-4176(200109)52:9<677::aid-maco677>3.0.co;2-d
Subject(s) - chloride , corrosion , chemistry , disproportionation , sodium , dissolution , buffer solution , inorganic chemistry , nuclear chemistry , catalysis , chromatography , biochemistry , organic chemistry
Abstract Dezincification behaviour of three commercial α‐brasses (33–37% Zn) in acetate buffer solutions containing 0.5 M sodium chloride was studied by weight loss, solution analysis and electrochemical polarization over a period of time extended for four weeks. The corrosion behaviour in the same solutions without chloride was also studied to explore the role of chloride in the dezincification. The presence of chloride led to a severe dezincification, which increased as time increased in contrast to chloride‐free solutions. The corrosion rate, however, was insensitive to the presence of chloride. The dezincification factor in chloride solutions increased in the order: pH 7.0 < pH 8.5 < pH 2.4 (order of increasing Zn dissolution rate) while the corrosion rate followed the order: pH 8.5 < pH 7.0 < pH 2.4 (order of increasing O 2 and H + reduction rates). Corrosion and dezincification was not a simple function of % Zn in the alloy. A model was proposed to explain the autocatalytic dezincification in chloride solutions and important elements in the model are: the production, disproportionation and redeposition of cuprous chloride complexes, growth of a spongy copper layer on the corroding alloy and establishment of an increasing number of microgalvanic cells.