Corrosion of stainless steels in acidic, neutral and alkaline saline media: Electrochemical and microscopic analysis

Abstract

This study presents how SS304 and SS316 corrode in saline media, including in the presence of acid and alkali, through an electrochemical and microscopic analysis. SS304 and SS316 samples were studied for their corrosion resistance in 1M NaCl, and in the presence of either 1M HCl or 1M NaOH. Potentiodynamic polarization studies were carried out to determine the corrosion potentials and currents. From the anodic polarization, regions corresponding to corrosion, passivation and transpassivation were identified. Samples were corroded at different anodic potentials corresponding to the different regimes and were analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). In 1M NaCl medium, SS304 exhibits pitting and passivation whereas SS316 does not. Transpassivation occurs through intergranular corrosion that connects the different pits. Making the medium acidic results in much higher corrosion rates for both SS304 and SS316, but the corroded surfaces bear vastly different structures. SS304 surface forms deep pits with large intergranular cracks resembling chimney stacks. However, SS316 surfaces show dendritic morphologies of deposited corrosion products, further evidenced by a higher O/Fe ratio in EDX measurements. In alkaline media, SS304 shows evidence of pits on whose edges corrosion products are deposited while no significant pitting is seen with SS316.

Effects of Austempering on the Microstructure, Corrosion and Mechanical Properties of AISI 1018 Steel

“…6c). The drastic reduction in weight loss is not unusual because corrosion in acidic environments has been shown to be generally more severe than in alkaline media [30]. Unlike the activity of H + from the 0.5M HCl on the alloy elements, the aqueous NaOH (0.5M) species only interacts with a few of the alloy elements, i. e. Diffusion and the resultant trapping of the alloy elements as well as increase in the interatomic bond over the heat treatment process leading to the improved mechanical properties of the austempered AISI 1018 specimen from the microstructural transformation also lead to a consequential reduction in the tendency of both Zn and Al alloys the react with the NaOH species in the alkaline media.…”

Effects of Film Thickness of ALD-Deposited Al2O3, ZrO2 and HfO2 Nano-Layers on the Corrosion Resistance of Ti(N,O)-Coated Stainless Steel

“…Furthermore, we used an accelerated corrosion test using saline, acidic, and oxidising solution. To our knowledge, there are few examples of tests carried out in such corrosive solutions [40][41][42] on ALD-coated supports. The corrosion protection behaviour of the fabricated coatings was assessed by potentiodynamic polarisation tests in a simulated corrosive environment (0.9% NaCl + 6% H 2 O 2 , pH = 4).…”

Erosive and corrosive wear performance and characterization studies of plasma‐sprayed WC/Cr 3 C 2 coating on SS316

“…Tungsten carbide (WC) or chromium carbide (Cr 3 C 2 ), or a combination of these materials, are the most commonly used carbide-based thermal spray coatings. [1][2][3][4][5] Some studies reported that WC-based coatings exhibited better erosion resistance to the steel and Ni-based substrate material. WC-Co-based coatings protected the steel substrates from wet and dry abrasion conditions and also observed that finer WC particles were associated with increased wear resistance.…”

“…Many researchers have performed substantial research into the elements that influence erosion, erosion mechanisms, and material erosion resistance to combat erosion. Tungsten carbide (WC) or chromium carbide (Cr 3 C 2 ), or a combination of these materials, are the most commonly used carbide‐based thermal spray coatings 1–5 . Some studies reported that WC‐based coatings exhibited better erosion resistance to the steel and Ni‐based substrate material.…”