Pitting corrosion of pipeline steel in dilute bicarbonate solution with chloride ions

Journal Article · Thu Sep 01 04:00:00 EDT 1994 · Corrosion (Houston); (United States)

DOI:https://doi.org/10.5006/1.3293540· OSTI ID:6841866

Mao, X; Liu, X ^[1]; Revie, R W ^[2]

---

1. Univ. of Calgary, Alberta (Canada). Dept. of Mechanical Engineering
2. Canada Centre for Mineral and Energy Technology, Ottawa, Ontario (Canada). Metals Technology Labs.

Corrosion behavior of grade 550 (X-80) pipeline steel with coating disbondments was studied in a range of bicarbonate (HCO[sub 3][sup [minus]]) solutions using a potentiodynamic polarization technique. Corrosion morphology of the steel was examined using optical and scanning electron microscopy. The shape of the polarization curves and the sensitivity of the steel to pitting corrosion varied with HCO[sub 3][sup [minus]] concentration. Increases in HCO[sub 3][sup [minus]] concentration resulted in a wider passive region and a more noble breakdown potential (E[sub b]), resulting in greater resistance to pitting corrosion. Surface morphology showed no pit formation in solutions with HCO[sub 3][sup [minus]] concentration > 0.05 M, but pits developed at a concentration of 0.05 M. Size and density of corrosion pits increased with further decreases in HCO[sub 3][sup [minus]] concentration. The graph of corrosion potential (E[sub corr]) vs HCO[sub 3][sup [minus]] concentration showed a peak at 0.05, whereas the corrosion current density increased monotonically with increased HCO[sub 3][sup [minus]] concentration. Low concentrations of chloride ion (Cl[sup [minus]]) greatly affected polarization characteristics and caused elimination of passivity in specific solutions.

• OSTI ID: 6841866
• Journal Information: Corrosion (Houston); (United States), Journal Name: Corrosion (Houston); (United States) Vol. 50:9; ISSN 0010-9312; ISSN CORRAK
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
42 ENGINEERING
420205 -- Engineering-- Transport & Storage Facilities-- (1980-)
ACID CARBONATES
ALLOYS
CARBON STEELS
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
CONCENTRATION RATIO
CORROSION
CORROSIVE EFFECTS
ELECTRIC POTENTIAL
HALIDES
HALOGEN COMPOUNDS
IRON ALLOYS
IRON BASE ALLOYS
PIPELINES
PITTING CORROSION
STEELS