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Corrosion and passivity of Hastelloy C4 in a high salinity brine
Author(s) -
Thies A.,
Schultze J. W.
Publication year - 1996
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/maco.19960470305
Subject(s) - brine , passivation , corrosion , materials science , passivity , electrolyte , oxide , metallurgy , electrochemistry , alloy , chromium , hardfacing , molybdenum , x ray photoelectron spectroscopy , high temperature corrosion , chloride , inorganic chemistry , electrode , chemical engineering , layer (electronics) , chemistry , composite material , organic chemistry , electrical engineering , engineering
Corrosion and passivity of Hastelloy C4 in Q‐brine, a magnesium chloride rich brine of pH 4.5 at room temperature, was studied by potentiodynamic (i(U) and C(U)) or potentiostatic polarisation. While the alloy rests passive at room temperature, no coherent, protecting passive layer is formed at temperatures above 60°C and potentials exceeding 0.2 V SHE. XPS analysis shows that at the rest potential and temperatures below 110°C, the oxide layer is about 1 nm thick and composed of chromium and molybdenum oxides without incorporation of Mg 2+ or Cl − from the electrolyte. At 200°C, its thickness increases 20 nm after 4 days and Mg + inclusions are found. Across the weld, Scanning Reference Electrode measurements in dilute NaCl showed a homogeneous potential distribution indicating that bulk material, heat affected zone and weld have the same electrochemical properties.