Stainless Steel In H2SO4 Solution Research Articles

Electrochemical behavior of additively manufactured 316L stainless steel in H2SO4 solution containing methionine as an amino acid

In this work, electrochemical and surface characteristics of 316L stainless steel manufactured by laser powder bed fusion (LPBF) were studied in the 0.1 M H2SO4 solution containing methionine as a corrosion inhibitor. Electrochemical studies such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and adsorption isotherm, and characterization methods such as field emission scanning electron microscopy integrated with an energy dispersive x-ray spectroscopy (FESEM‐EDS), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) were performed to evaluate the effect of the inhibitor on the corrosion behavior of LPBF processed stainless steel. FESEM micrographs of the LPBF processed alloy showed the presence of cellular/columnar morphology, most probably due to the effect of a high cooling rate during the LPBF process. The results of the electrochemical tests indicated that the charge transfer resistance of stainless steel in the presence of methionine increases from 4810 up to 13,300 Ω cm2, and Ecorr shifted about 250 mV toward the noble direction. Besides, corrosion current density decreases from 3.24 to 0.45 μA cm−2 as the concentration of methionine increases from 0 to 500 ppm in the sulfuric acid. Adsorption isotherm revealed a physical-chemical interaction of inhibitor with the surface. It is assumed that the methionine can adsorb on the anodic sites of the alloy during the immersion period and block the immigration of aggressive species toward the surface.

Corrosion Inhibition of Honeycomb Waste Extracts for 304 Stainless Steel in Sulfuric Acid Solution.

The extract of honeycomb waste was studied as a corrosion inhibitor on 304 stainless steel in H2SO4 solutions. The honeycomb waste was obtained from beekeeping at Lawang-Malang, East Java, Indonesia. Electrochemical and scanning electron microscopy methods were used to investigate the performance of the corrosion inhibition process. The inhibition efficiency of the inhibitor (2000 mg/L) reached 97.29% in 0.5 M H2SO4 and decreased with the acid concentration. Kinetic parameters were calculated to explain the effect of acid concentration on the inhibition process. The study on the adsorption behavior of the extracts followed the Frumkin isotherm model. The adsorption of the inhibitor on the 304 stainless steel surface was confirmed by the negative and lower values of Gibbs free energy. The obtained scanning electron microscopy (SEM) images were confirmed by comparing the surface of the specimens with and without inhibitor after corroding for one week. The results indicated that the extract acted as a good inhibitor for 304 stainless steel in acid corrosion.

Research on Corrosion Resistance of Titanizing and Nitriding on Carbon Steel in H<sub>2</sub>SO<sub>4 </sub>Solution

Q195 steel was treated with titanizing followed plasma nitriding by glow plasma alloying technology using single pulse power supply. The corrosion resistances of titanizing sample and titanizing + ion nitrided sample were studied. The results show that the alloying layer is 200 μm in depth and organization is α-Fe solid solution containing Ti by plasma titanizing technology using single pulse power supply. An obvious reactive diffusion dividing line formed between alloying layer and the substrate. It shows that diffusion phenomenon happened in process of titanizing. The morphology of Ti alloy layer was columnar crystals. The content of Ti on the surface is up to 5 wt%. And the Ti content of alloying layer is in a decreasing from the surface to the inner on a gradient distribution. The phase structure of titanizing layer is composed of Fe2Ti, Fe-Ti and TiC phases. The phase structure of titanizing + ion nitrided sample was obviously TiN phase and a few Fe-Ti phase. The surface hardness of untreated carbon steel is 110 HV and that of the alloying layer of titanizing is 310HV. The surface hardness of titanizing + ion nitrided sample is 1800HV. The corrosion resistance of titanizing sample is increased 12.15 times compared with the untreated sample and 1.42 times compared with 18-8 stainless steel in H2SO4solution; The corrosion resistance of titanizing + ion nitrided sample is increased 7.444 times compared with the untreated sample and as well as 18-8 stainless steel in H2SO4solution.

Thioamide Compounds as Corrosion Inhibitors for Stainless Steel in H2SO4 Solution

Abstract The influence of organic compounds on the corrosion of stainless steel in 0.5 M sulfuric acid (H2SO4) was investigated using weight-loss and potentiodynamic polarization techniques, as well as open-cirucuit potential (OCP) measurements. The nature of the film formed and the adsorption mechanism, as well as thermochemical parameters involved, were explored and expounded. This investigation indicated that the inhibition efficiency increases with increasing the concentration of organic compounds. The inhibitors are of the mixed type but dominantly act as anodic in 0.5 M H2SO4. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the surface and examine the morphology of the Type 304 (UNS S30400) stainless steel under ordinary acid attack with that formed under inhibited conditions. The adsorption of the inhibitors was expressed reasonably by the Langmuir adsorption isotherm. The calculated activation energy and thermodynamic parameters point to a mixed adsorption pattern of inhibitor molecules, with physical adsorption as the dominant mode.

XPS Analysis of Passive Film on Stainless Steel

Potentiodynamic, impedance measurements were carried out on 304 stainless steel in 0.5N, 1.0, 2.0 and 5.0 N H2SO4 solutions. X-ray photoelectron spectroscopic (XPS) studies carried out on 304 stainless steel in H2SO4 solutions revealed the existence of CrOOH, Cr2O3,  -Fe2O3, - FeOOH, Mn2O3, Mn3O4, MnS, Ni (OH)2, Ni2O3, NiO, sulphides. The passive film found to contain chromium oxide inner layer and the dissolution of iron through it caused the formation of oxides of iron namely  - Fe2O3 and -FeOOH. Higher oxides of manganese and nickel are also due to dissolution through the film. Sulphates are reduced to sulphur chemically by the released protons from anodic polarization.

Effect of Cl−on the corrosive wear of AISI 321 stainless steel in H2SO4 solution

The effect of Cl− on the corrosive wear behaviour of AISI 321 stainless steel in H2SO4 solution was studied via the corrosive wear rate, the load bearing capacity of passive film and the relationship between pitting and corrosive wear. There is a critical load at natural potential, below which the corrosive wear rate is slightly lowered by Cl−, while above which is increased. At natural potential there are more pits at low load than that at a higher one in the wear tracks and the pits are also deeper. The load bearing capacity is lowered by Cl− at passive region and then the corrosive wear rate increased.

Sol-gel TiO2-SiO2 films as protective coatings against corrosion of 316L stainless steel in H2SO4 solutions

Sol-gel TiO2-SiO2 films were deposited on 316L stainless steel by dip coating process from a sono-catalysed sol of composition 30TiO2-70SiO2 prepared from a mixture of Ti(OC2H5)4 and Si(OC2H5)4, absolute ethanol C2H5OH and glacial acetic acid CH3COOH as precursors and solvents. The films, densified at 800° C in air for 2 h, are composed of small orthorhombic titania (anatase) crystallites embedded in a SiO2 amorphous matrix as identified by X-ray diffraction. The temperature dependence of the film morphology was observed using scanning electron microscopy (SEM) and the content was determined by FTIR reflection spectroscopy. The corrosion behaviour of 316L stainless steel samples coated with densified 30TiO2-70SiO2 films was studied in 15% H2SO4 by potentiodynamic polarization curves at 25, 40 and 50°C. The measured corrosion rates show a considerable decrease for the protected steel samples in comparison to the bare substrate. The effect of time of heat treatment of the films on the corrosion parameters is also reported.

Inhibiting Effects of Ethanethiol, Dimethyl Sulfide, and Dimethyl Disulfide on the Corrosion of Stainless Steel (405) in Sulfuric Acid

Abstract The corrosion behavior of stainless steel (405) specimen in 5 M H2SO4 solution has been investigated potentiostatically at four temperatures in the range 303–323 K. The inhibiting effects of ethanethiol (EtSH), dimethyl sulfide (Me2S), and dimethyl disulfide (Me2S2) have thereafter been tested for four inhibitor concentrations of 0.5, 1, 5, and 10 mmol dm−3. The sulfur compound addition to the H2SO4 solution caused a shift, mainly in the cathodic direction, of the corrosion potential, the electrode potential at low current densities as well as of the linear section of the cathodic Tafel line. The protection efficiency of each sulfur compound was determined at various temperatures and inhibitor concentrations. The sulfur compound acted as a corrosion inhibitor in the H2SO4 solution through adsorption on the stainless steel surface. The kinetic results, operating through a compensation effect, could well account for the variation of the inhibiting capacities of the various sulfur compounds. The results indicated that inhibition process involved the shift of the stainless steel corrosion to those surface sites which are associated with progressively higher energy of activation. EtSH was the most efficient of the three sulfur compounds for inhibiting the corrosion of the stainless steel in H2SO4 solution.

Straining Metal Electrode Technique as a SCC Test—Type 304 Stainless Steel in NaCl + H2SO4Solutions

Abstract The straining metal electrode technique was applied to the study of stress corrosion cracking (SCC) susceptibility of Type 304 austenitic stainless steel in H2SO4 solutions and in H2SO4 + NaCl solutions, at room temperature. A film formation process was detected in the active zone of Type 304 in H2SO4 + NaCl solutions. It was concluded that a film rupture mechanism operates during SCC of this metal in H2SO4 + NaCl solutions. The crack propagation rate values and the crack morphologies predicted by straining experiments were found to be in very good correlation with those found by conventional SCC tests.

Hydrogen Permeability in a Stable Austenitic Stainless Steel

Abstract Tests at 21 C (69 F) show hydrogen enters and penetrates thin Type 310 stainless steel in H2SO4 solution under applied cathodic currents, first condition for hydrogen entry contributing to hydrogen embrittlement and stress corrosion cracking. When metal surface is passive permeation rate depends on applied current density; when active, rate depends on surface corrosion currents and applied current.