Modeling the Effects of Crevice Former, Particulates, and the Evolving Surface Profile in Crevice Corrosion

Abstract

Crevice corrosion may initiate in confined regions due to transport limitations, followed by an accumulation of a highly corrosive chemistry, capable of dissolving the metal. The metal and the crevice former surface roughness, the presence of particulates under the crevice former and the accumulation of solid corrosion products at the corroding site would significantly affect the current and potential distribution at the anode by increasing the ohmic potential drop. Most crevice corrosion models focus on a smooth walled crevice of uniform gap and do not account for the changing profile after crevice corrosion has been initiated. In this work we analyze the crevice (anodic) region and apply current and potential distribution models to examine the effects of the perturbed surface topography. The analysis focuses on three related issues: (i) the effects of surface roughness of the metal and the crevice former, (ii) the effects of particulates under the crevice former, and (iii) the evolution of the crevice profile with corrosion product accumulation at the active, anodic region.

Characterization of the Corrosion Products of Crevice Corroded Alloy 22

“…1 Localized corrosion is an important degradation mode to be evaluated for the corrosion performance of Alloy 22 over long exposure periods, and it has been examined by a number of researchers. [3][4][5][6][7][8][9][10][11][12][13] Many factors affecting the localized corrosion behavior of Alloy 22 have been studied, such as the effects of Cl − and oxyanions, 3,4,[14][15][16] the effects of potential and temperature, 5,17 and the propagation and stifling of the crevice corrosion. 5,9,18,19 During the crevice corrosion process, corrosion products are formed.…”

“…The insoluble corrosion products formed in the crevice can increase the ohmic resistance, and they can also affect transport in solution. The increase in ohmic resistance changes the potential distribution in the crevice, 11,20 and this is an important factor for the initiation and propagation of crevice corrosion. 21,22 The objective of this work was to investigate the composition of corroded metal surfaces and the corrosion products formed by the crevice corrosion of Alloy 22.…”

Crevice Corrosion Damage Evolution in High Temperature Brines

“…A number of the processes that pertain to an operating crevice corrosion cell are illustrated in Figure 3 [9]. These processes include: electrochemical effects, migration, diffusion, anodic dissolution, critical crevice chemistry, corrosion products and deposition, precipitation and cathodic reduction.…”

“…After the constant potential, crevice corrosion tests where crevice corrosion damage was observed, there were solid corrosion products under the crevice contact where corrosion had occurred and corrosion products deposited on the metal surface just outside of the crevice contact area. Photomicrographs of the corrosion products associated with a crevice contact area are shown in figure 7 [9] . The black corrosion products were loosely bound to the metal surface and comprised of compacted particulate.…”

Modeling Particulates Effects on the Cathode Current Capacity in Crevice Corrosion

“…In corroding systems, the anode imposes a total current demand, depending upon its size, shape, and dissolution kinetics. 5,6 In order to sustain the corrosion process, the external exposed cathodic surface must provide this current. The cathode capacity ͑to sustain corrosion͒ depends primarily on the electrolyte properties and on the oxygen-reduction kinetics on the cathode surface.…”