TY - BOOK

T1 - Depassivation and Repassivation of Stainless Steels

AU - Mujanović, Emir

N1 - no embargo

PY - 2020

Y1 - 2020

N2 - In oil and gas production, deep wells producing highly aggressive media are often completed with highly alloyed corrosion resistant alloys (CRAs, mainly steels). These CRAs have excellent corrosion properties due to the formation of a passive layer of chromium, iron and molybdenum oxides and hydroxides. During acidizing jobs, when a plugged well is re-opened, and during sand production at high flow velocities, localized or uniform depassivation can occur and yield high corrosion rates of used CRAs. In the present work the resistance of passive layers of various stainless steels was investigated alongside the conditions and kinetics of when these layers are rebuilt. Methods applied consisted of: potentiodynamic experiments, immersion tests, scratch tests and variable pH flow experiments. Results revealed that, with the exception of those with very low alloys, all stainless steels showed repassivation after acidizing when the pH level increased above 3. Repassivation occurs within 100 s to a certain (sufficient) extent, although the passive layer is not completely rebuilt within this period.

AB - In oil and gas production, deep wells producing highly aggressive media are often completed with highly alloyed corrosion resistant alloys (CRAs, mainly steels). These CRAs have excellent corrosion properties due to the formation of a passive layer of chromium, iron and molybdenum oxides and hydroxides. During acidizing jobs, when a plugged well is re-opened, and during sand production at high flow velocities, localized or uniform depassivation can occur and yield high corrosion rates of used CRAs. In the present work the resistance of passive layers of various stainless steels was investigated alongside the conditions and kinetics of when these layers are rebuilt. Methods applied consisted of: potentiodynamic experiments, immersion tests, scratch tests and variable pH flow experiments. Results revealed that, with the exception of those with very low alloys, all stainless steels showed repassivation after acidizing when the pH level increased above 3. Repassivation occurs within 100 s to a certain (sufficient) extent, although the passive layer is not completely rebuilt within this period.

KW - Stainless steel

KW - Depassivation

KW - Repassivation

KW - Scratch test

KW - Mechanical depassivation

KW - Chemical depassivation

KW - Repassivierung

KW - chemisch beständiger Stahl

KW - Lochkorrosion

KW - gleichförmige Korrosion

KW - Kratztests

M3 - Doctoral Thesis

ER -