Using pitting and protection potentials to predict pitting behavior: New insights

Technical Report · Tue Oct 01 00:00:00 EDT 1991

OSTI ID:5158676

A literature review was performed to identify test methods that have been used to examine pitting susceptibility of alloys in chloride (Cl{sup {minus}}) containing environments. Several techniques were identified and a critical analysis of the validity of the different electrochemical methods was performed with special attention given to the causes of variations observed in the pitting, or breakdown, potential (E{sub pit}) and the protection, or repassivation, potential (E{sub prot}). Experiments were performed on Type 317L stainless steel in three solutions containing high levels of Cl{sup {minus}} and Alloy G3 in two solutions containing high levels of Cl{sup {minus}}. The test solutions were designed to simulate environments present in flue gas desulfurization systems. Cyclic potentiodynamic polarization (CPP) experiments and constant potential-time experiments (up to 60 days) were performed to examine pit initiation and repassivation; and modified ASTM F-746 tests were performed to establish the protection potential as a function of prior pitting history. Analysis of the data suggests that there exists a unique pitting potential (E{sub u}) defined by the stochastic models for pit initiation that equals the most active value of E{sub pit} (long incubation times) and that equals the most noble E{sub prot} value (measured following only minimal pit growth). 24 refs., 34 figs., 7 tabs.

• Research Organization: Electric Power Research Inst., Palo Alto, CA (United States); Cortest Columbus Technologies, OH (United States)
• Sponsoring Organization: EPRI; Electric Power Research Inst., Palo Alto, CA (United States)
• OSTI ID: 5158676
• Report Number(s): EPRI-EAR-7489
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STAINLESS STEEL-317
PITTING CORROSION
CHLORINE
CORROSION RESISTANCE
ELECTROCHEMISTRY
POLARIZATION
POTENTIALS
ALLOYS
CHEMICAL REACTIONS
CHEMISTRY
CORROSION
ELEMENTS
HALOGENS
HIGH ALLOY STEELS
IRON ALLOYS
IRON BASE ALLOYS
NONMETALS
STAINLESS STEELS
STEELS
360105* - Metals & Alloys- Corrosion & Erosion