Effect of Environmental Variables on Localized Corrosion of Carbon Steel

• Published in: Corrosion (Houston, Tex.) Vol. 56; no. 5; pp. 505 - 514
• Main Authors: Brossia, C.S., Cragnolino, G.A.
• Format: Journal Article
• Language: English
• Published: Houston, TX NACE International 01.05.2000; NACE
• Subjects: Applied sciences; Carbon steel; CARBON STEELS; Carbonates; CHLORIDES; Circuits; Construction materials; Containers; CORROSION; Corrosion effects; Corrosion environments; Corrosion resistance; Corrosion resistant steels; Corrosion tests; Cracks; ELECTRIC POTENTIAL; ENVIRONMENT; Environmental conditions; Environmental effects; Exact sciences and technology; GROUND WATER; Groundwater; High level radioactive wastes; Localized corrosion; MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; MATERIALS SCIENCE; Metals. Metallurgy; pH effects; PH VALUE; RADIOACTIVE WASTE DISPOSAL; Radioactive wastes; Repassivation; Steel; Steel construction; Waste disposal; Corrosion resistance; Passivation potential; Corrosion; Corrosion test; Repassivation; Localized corrosion; Environmental effect; Carbon steel; Steel; Experimental study
• ISSN: 0010-9312; 1938-159X
• DOI: 10.5006/1.3280555

ABSTRACTCarbon steels are among the most widely utilized engineering materials for structural applications. As such, their corrosion performance under a wide variety of environmental conditions has been examined, and in many cases, only uniform corrosion has been observed. Because carbon steel generally undergoes relatively predictable uniform dissolution in many environments and is a widely utilized engineered material in structural applications, it was chosen by the U.S. Department of Energy (DOE) as a potential candidate corrosion-allowance material for high-level nuclear waste (HLW) disposal containers.1-2 There are a number of environmental factors, however, that can cause carbon steel to undergo rapid, localized corrosion instead of relatively slow, uniform corrosion. For localized corrosion, pit initiation potential (Epit), commonly measured by scanning or stepping the potential, is the potential above which stable pit growth is detected.3 Even though pits may be initiated well below this potential, spontaneous repassivation occurs and pits fail to continue propagating, thus leading to their classification as metastable pits. Metastable pitting is of fundamental importance to the understanding of localized corrosion dynamics. Generally, it is not important for life prediction as these pits do not lead to perforation of the structure. Furthermore, the potential to repassivate stably growing pits (repassivation potential, Erp) is approximately equal to Epit, provided the former is measured for deep pits under slow, backward scan rates and the latter is measured under extremely long exposure conditions.4 Thus, Erp can serve as a conservative estimate of the minimum potential necessary for nucleation and stabilization of localized corrosion. Erp and Epit generally are used to evaluate effects of environmental variables on the localized corrosion behavior of materials during short-term tests.