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Passivation of HAZ s of API ‐ X 100 pipeline steel in bicarbonate‐carbonate solutions at 298 K
Author(s) -
Eliyan F. F.,
Icre F.,
Alfantazi A.
Publication year - 2014
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.201206985
Subject(s) - passivation , carbonate , bicarbonate , chemistry , chloride , electrochemistry , inorganic chemistry , electrode , organic chemistry , layer (electronics)
This research explores electrochemical correlations between heat‐affected zones (HAZs), produced by Gleeble © thermal simulation cycles, and their passivation behavior in bicarbonate–carbonate solutions. The investigations were carried out in comparison with the base API‐X100 steel in naturally aerated 0.5 g/L chloride solutions, containing a matrix of bicarbonate and carbonate concentrations at 298 K. The slow 0.05 mV/s potentiodynamic scans revealed that the passivation onsets earlier in proportion with the bicarbonate concentrations, possessing accordingly greater immunity against chloride ions on HAZs cooled at 10 and 60 K/s from 1223 K peak temperature. The HAZs cooled at 10 K/s, particularly in concentrated carbonate solutions, showed the most stable passivation, and the HAZs cooled at 60 K/s showed the lowest cathodic activity regardless of the chemical conditions. −0.1 V, versus saturated calomel electrode, potentiostatic currents and the open‐circuit potentials decreased and increased, respectively, with the carbonate concentration, confirming with the main potentiodynamic polarization results, and a corresponding passivation behavior of the HAZs, regardless of a bicarbonate–carbonate condition, was relatively similar. In contrary to the 60 K/s HAZs, the 10 K/s HAZs showed evidence of growing passive films with time and high charge‐transfer resistance, as measured by the EIS tests.