Long-term effects of humidity on stainless steel pitting in sea salt exposures

February 25, 2021

Jayendran Srinivasan (1), Tim Weirich (1), G. A. Marino (1), A. R. Annerino (1), J. M. Taylor (1), Philip Noell (2), James Griego (2), R. F. Schaller (2), Charles Bryan (2), Jenifer Locke (1), Eric Schindelholz (1)
Journal of The Electrochemical Society, 168, Issue 2, February 2021. DOI: 10.1149/1945-7111/abdc75


Ground 304 stainless steel (SS) samples were exposed to sea salt particles at 35 °C and two relative humidity (RH) levels for durations ranging from 1 week to 2 years. For all exposure times, pit number density and total pit volume at 40% RH were observed to be considerably greater than those at 76% RH. Statistical analysis of distributions of pit populations for both RH conditions showed that pit number density and total pit volume increased rapidly at first but slowed as exposure time increased. Cross-hatched features were observed in the 40% RH pits while ellipsoidal, faceted pits were observed at 76% RH. Optical profilometry indicated that most pits were not hemispherical. X-ray tomography provided evidence of undercutting and fissures. Piecewise curve fitting modeled the 40% RH data closely, predicting that corrosion damage would eventually plateau. However, a similar treatment of the 76% RH data suggested that corrosion damage would continuously increase, which implied that the piecewise power-law fit was limited in its ability to model atmospheric corrosion generally. Based on these observations, the operative mechanisms determining long-term corrosion behavior were hypothesized to be different depending on the RH of exposure.

How Our Software Was Used

Dragonfly was used to process reconstructed XCT datasets.

Author Affiliation

(1) Fontana Corrosion Center, Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210, United States of America.
(2) Materials Science and Engineering, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States of America.