Measurement of Corrosion Potential Under Thin Electrolyte Films and the Expression of Localized Corrosion Damage
Abstract
An analysis of cracking in vent holes in high-strength steel tubes is reported, with the predictions being judged to be highly conservative. Pitting and subsequent cracking is attributed to localized corrosion beneath a layer residue on the hole surface that accumulates with use. The residue contains a high concentration of chloride ion, which is well-known to be a powerful agent in affecting passivity breakdown and pitting on high strength steels, like AISI 4335. The measured corrosion potential at three locations on a AISI 4335 sample in contact with a thin slurry of residue under prototypical field conditions was found to be -0.255 0.021 Vshe. Because this value is close to the breakdown potential (which was not measured under exactly the same conditions) the electrochemical conditions are therefore judged to be conducive to passivity breakdown and hence pitting corrosion. The stress state of the region as determined by finite elementanalysis, is also judged to be conducive to the nucleation of cracks from pits. Using Damage Function Analysis (DFA) and a Pareto distribution for crack growth rate, the study successfully accounts for the evolution of localized corrosion damage and provides an effective means of extrapolating damage to future times, if the environmental conditions remain constant. The impact of stress transients during service on the accumulation of the observed damage (crack length) is judged to be negligible.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2019
- Accession Number
- AD1123259
Entities
People
- Andrew G. Littlefield
- Daniel P. Schmidt
- Digby D. Macdonald
- Edward J Troiano
- George R Engelhardt
- Gregory N. Vigilante
- Jennifer A Cordes
- John J. Cannon
- Robert E Dillon
Organizations
- University of California, Berkeley