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Effect of Co and W on the corrosion behaviour of 1% Cr steel in flowing synthetic seawater
Author(s) -
Choi YoonSeak,
Shim JaeJoo,
Kim JungGu
Publication year - 2004
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.200303725
Subject(s) - corrosion , dielectric spectroscopy , electron microprobe , x ray photoelectron spectroscopy , materials science , nyquist plot , metallurgy , artificial seawater , aqueous solution , rust (programming language) , seawater , oxide , analytical chemistry (journal) , nuclear chemistry , electrochemistry , chemistry , chemical engineering , electrode , chromatography , oceanography , computer science , engineering , programming language , geology
The aqueous corrosion characteristics of 1% Cr‐steel alloyed with small amounts of Co and W in synthetic seawater was studied by using immersion weight‐loss tests, electrochemical corrosion tests (potentiodynamic tests and electrochemical impedance spectroscopy (EIS) measurements) and analytical techniques. 1% Cr steels containing Co or W from 0.2 to 0.4 wt.% showed higher corrosion resistance than the 1% Cr steel in the immersion and potentiodynamic tests. EIS measurements showed that the Nyquist plot presented one time constant. Furthermore, the Co‐ and W‐bearing steels present higher R p values than the 1% Cr steel through all the test period. The better corrosion resistance of the Co‐and W‐bearing steels is attributed to the protectiveness of the surface layer. The corrosion products were examined using electron probe microanalysis (EPMA) and X‐ray photoelectron spectroscopy (XPS). The results of EPMA indicated that Cr was concentrated in the inner region of the rust layer, while Co and W were distributed all over the rust layer. XPS results showed that Co existed as a trivalent oxide in the rust layer and W in the rust appeared in the form of a WO 4 compound. These compounds act as a factor for corrosion resistance in aqueous solutions.