Stainless Steel In Sulphuric Acid Research Articles

Garlic Extract as an Environmentally Corrosion Inhibitor of API X60 Carbon Steel and 316L Stainless Steel in Sulphuric Acid

Garlic Extract as an Environmentally Corrosion Inhibitor of API X60 Carbon Steel and 316L Stainless Steel in Sulphuric Acid

Effects of stirring action during friction on electrode processes of AISI 304 stainless steel in sulphuric acid

It is known that tribology contact can accelerate the anodic reaction in alloys with passive films. Less attention has been paid in the literature on the cathodic reaction in materials under tribology contact. An AISI 304 stainless steel surface was subjected to linear reciprocating sliding friction in a 0.5 mol/L sulphuric acid solution. An integrated corrosion test cell with a wear tester was used. When stirring action was applied, an anodic shift of the OCP was observed. Stirring action also resulted in a cathodic shift of the measured current and polarity reversal when the sample was potentiostatically polarised at anodic potentials in the active region. An increase in current density was achieved by stirring when low cathodic potential was applied. Stirring, however, did not cause any significant change in current densities when a higher cathodic overpotential was applied. This was due to the bubble evolution-induced convection of the rapid precipitation of hydrogen bubbles accelerating mass transfer on the electrode surface. It was found that external stirring action could accelerate the kinetics of hydrogen evolution on the electrode surface in a state of slow hydrogen evolution. In addition, increased friction frequency could result in an increase in the amplitude of current transients.

Passivity of stainless steel in sulphuric acid under chemical oxidation

ABSTRACTThe main purpose of the present work was to study the passivity of stainless steel in sulphuric acid under chemical oxidation with H2O2 solution. Potentiodynamic polarisation and open circuit potential (OCP) measurements indicated that H2O2 facilitates the increase of OCP of stainless steel which shifts from active region into passive region. The X-ray photoelectron spectroscopy results suggested that a passive film, composed of oxyhydroxides, Cr2O3, Cr(VI) species, NiO, and sulphate (FeSO4, Cr2(SO4)3·xH2O), is achieved after H2SO4–H2O2 passivation. The passive mechanism under H2O2 oxidation was discussed and the corrosion resistance of passive film was compared with that of the passive films produced by HNO3 passivity and H2SO4 potentiostatic passivity. The results of electrochemical impedance spectroscopy, cyclic voltammetry, and anodic polarisation experiments confirmed that the chemical oxidation with H2O2 solution is capable of improving the corrosion resistance of stainless steel significantly and the passive film is more stable than those produced by other passivating methods.

Corrosion behaviour of ruthenium laser surface alloyed austenitic stainless steel in sulphuric acid and sodium chloride solutions

AISI 304L stainless steel was laser surface alloyed with ruthenium enriched 304L powder using a continuous wave Nd:YAG laser. Corrosion performance of the surface alloys was studied in 1 M sulphuric acid and 3.5 wt% sodium chloride at 25, 35 and 45 °C using potentiodynamic polarisation. The results showed that the presence of ruthenium decreased corrosion rates in both solutions and inhibited pitting in sodium chloride. High temperatures were particularly detrimental to the corrosion resistance of the alloys in sodium chloride, but were surprisingly beneficial in sulphuric acid; inducing spontaneous passivity and reducing corrosion current density from 129 μA/cm2 at 25 °C to about 0.5 μA/cm2 at 45 °C.

Corrosion resistance of austenitic stainless steel in sulphuric acid

The resistance and susceptibility of austenitic stainless steel, Type 304, exposed to strong tetraoxosulphate (VI) acids (2 and 5 M concentrations) contaminated with sodium chloride at ambient temperatures was investigated by gravimetric and metallographic/scanning electron microscopy surface characterization methods. Scanning electron microscope (SEM) was used to examine and characterize the test specimen’s surface morphology after immersion in the corrosive media. Surface corrosion deposit composition was analyzed with the SEM paired with energy dispersive spectrometer (EDS). This paper reports the observed severe general and pitting corrosion and the resistance of the steel to corrosion at different concentrations of the acid chloride media. The results obtained showed the weak corrosion resistance/appreciable corrosion susceptibility of the stainless steel alloy to the test environments.

EBSD, SEM and FIB characterisation of subsurface deformation during tribocorrosion of stainless steel in sulphuric acid

The tribocorrosion behaviour of a 304L stainless steel/alumina contact was investigated in sulphuric acid at two imposed potentials (cathodic and passive). The metal deformation below the surface was investigated by analyzing cross sections using secondary electron microscopy (SEM) and electron back scatter diffraction (EBSD). Cross sections were also prepared using focussed ion beam (FIB) and analyzed by in situ SEM. AES depth profiling was used to analyze surface composition. Metal subsurface deformation resulted in the build up of a deformed layer of approximately 20 μm thickness in the near surface zone within the wear track. This layer exhibited a deformation gradient with high deformation close to the surface resulting in grain refinement down to 10 nm. The applied potential influenced the deformation: at passive applied potential more strain was accumulated below the surface resulting in more pronounced grain refinement and higher density of defects. Using AES analysis no alumina transfer from the counter body or any significant burying of oxide below the surface could be detected.

Pitting corrosion resistance of coloured oxide films grown on stainless steel in sulphuric acid in the presence and absence of chromic acid

In this work, pitting corrosion resistance of coloured oxides films grown on AISI-304 stainless-steel in H2SO4 and H2SO4 + CrO3 was evaluated. Surface morphology and topography of the films were examined by SEM (scanning electron microscopy) and AFM (atomic force microscopy), respectively. Electrochemical characterizations were conducted by polarization curves and impedance measurements in borate buffer pH 9.2. The pitting corrosion was evaluated by polarization curves carried out in the same solution containing NaCl. All coloured films presented similar values of Epit, but they were higher than those for non-coloured ones. The values of (Epit - Ecor) were in the range of 0.45-0.57 V, 0.78-0.92 V and 0.98-1.12 V for native films and films grown in the presence and absence of chromic acid, respectively. Therefore, the films grown on stainless steel in the absence of chromic acid presented the highest potential range free of pitting corrosion.

Corrosion behavior and passive film chemistry of 216L stainless steel in sulphuric acid

Corrosion behavior and chemical structure of the passive film of a newly developed 200 series austenitic stainless steel (216L) were studied in sulfuric acid (H2SO4) and compared with 316L. From potentiodynamic polarization studies it was found that the corrosion behavior of 216L closely follows that of 316L. The breakdown of passivity was evaluated by addition of sodium chloride (NaCl). The immersion tests revealed that the corrosion rate of 216L in various concentrations of H2SO4 at ambient temperature is equivalent to 316L. X-ray photoelectron spectroscopy (XPS) analysis of the passive film formed on 216L revealed enrichment of Cr ions on the surface while Mo and N compounds were also present. Ni and Mn ions were conspicuous by their absence in the passive film.

Corrosion characteristics of polyaniline-coated 316L stainless steel in sulphuric acid containing fluoride

The corrosion resistance of conducting polyaniline (PANi) coatings deposited on 316L stainless steel (316L SS) at various cycle numbers of cyclic voltammetry (2-, 3- and 4-cycles) by electro-polymerization in sulphuric acid solution containing fluoride was investigated by electrochemical techniques. The corrosion resistance of the 316L SS substrate was considerably improved by the PANi coating. The increase of the cycle number of cyclic voltammetry increased the thickness and enhanced the performance of the PANi coating due to low porosity.

The effect of cysteine on the corrosion of 304L stainless steel in sulphuric acid

The effect of cysteine on the corrosion of 304L stainless steel in 1 mol l −1 H 2SO 4 was studied using open-circuit potential measurements, anodic polarization curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). All the electrochemical measurements obtained in the presence of low cysteine concentration (10 −6–10 −5 mol l −1) presented the same behaviour as those obtained in the absence of cysteine, a passivated steel surface. However, for higher cysteine concentrations (10 −4–10 −2 mol l −1), a different behaviour was observed: the corrosion potential stabilized at a more negative value; an active region was observed in the anodic polarization curves and the electrochemical impedance diagrams showed an inductive loop at lower frequencies and a much lower polarization resistance. These results show that the presence of cysteine at high concentration turns the surface of 304L stainless steel electrochemically active, probably dissolving the passivation layer and promoting the stainless steel anodic dissolution. SEM experiments performed after immersion experiments at corrosion potential were in good agreement with the electrochemical results.

The effect of mechanical and electrochemical parameters on the tribocorrosion rate of stainless steel in sulphuric acid

The tribocorrosion behaviour of a passive AISI430 ferritic stainless steel sliding against alumina in 0.5 M sulphuric acid has been studied using a tribometer that allowed for electrochemical measurements. The effects of applied potential, normal load, sliding velocity, sliding distance and alumina roughness on the friction, wear volume and anodic current were determined. The obtained results are interpreted in terms of a previously proposed theoretical model describing the average current in terms of depassivation rate and repassivation charge, taking into account the role of non-electrochemical parameters such as applied normal force, sliding velocity, metal hardness and contact configuration. Under the experimental conditions of the present study, the depassivation rate was found to govern the measured anodic current. Consideration of how mechanical and operational parameters affect the depassivation rate led to a consistent description of their effect on the tribocorrosion rate in accordance with the proposed model.

The influence of various major and minor alloying elements on the corrosion of an Fe‐40 %Cr Superferritic stainless steel in sulphuric acid

AbstractThe corrosion resistance of an Fe‐40%Cr superferritic alloy containing various major and minor alloying additions, e. g. nickel, molybdenum, aluminium, zirconium, nitrogen, niobium, titanium and ruthenium, as well as various combinations of them, was investigated in dilute sulphuric acid. Although small nickel and molybdenum additions alone cannot cause spontaneous passivation of the Fe‐40%Cr alloy to which they are added, a combination of these two alloying elements result in an Fc‐40%‐Cr superferritic stainless steel which can passivated spontaneously in dilute sulphuric acid. Further additions of minor alloying elements like Ti, Nb, Ru and N have an influence on the time required to achieve spontaneous passivation and the final open‐circuit potential eventually reached. Further additions of Al and Zr to the Fe‐40%Cr‐2%Ni‐2%Mo alloy did not have much of an effect on the final open‐circuit potential reached, and only affected the time required before this potential was reached in each case.

Effect of copper additions on corrosion of stainless steel in sulphuric acid : M.D.M. Neves et al (Inst. Pesquisas Energeticas e Nucleares, Sao Paulo, Brazil)

Effect of copper additions on corrosion of stainless steel in sulphuric acid : M.D.M. Neves et al (Inst. Pesquisas Energeticas e Nucleares, Sao Paulo, Brazil)

Effects of alternating voltage modulated passivation on passive film on 18Cr–9Ni–lTi stainless steel

The effects of alternating voltage (av) modulated passivation on the properties of the passive film formed on 18Cr–9Ni–1Ti stainless steel in sulphuric acid have been investigated by ellipsometry, the potential step technique, Auger surface analysis, and potentiostatic cathodic reduction. It has been found that av modulated passivation can increase the passive film thickness and alters its cathodic reduction behaviour; the chemical dissolution characteristics are also affected. An increase in the breakdown potential of the film is achieved with some amplitudes of av modulation.

Effects of Vapour Deposited and Bulk Alloyed Ruthenium on Corrosion Resistance of a Duplex Stainless Steel in Sulphuric Acid

An investigation was carried out to assess the corrosion resistance of duplex stainless steel that was surface alloyed with ruthenium. It was found that vapour deposited ruthenium on the surface of a duplex stainless steel improved the corrosion resistance, especially if the alloy is annealed after surface deposition has been carried out. The ruthenium apparently increases the corrosion potential to more noble values, and also inhibits anodic dissolution. This method promised a more economical technique of cathodic modification than bulk alloying.

Corrosion Behaviour of Sintered Stainless Steel in Sulphuric Acid and Sodium Chloride Solutions

Corrosion Behaviour of Sintered Stainless Steel in Sulphuric Acid and Sodium Chloride Solutions

Testing for the Limit of Stable Passivity of Stainless Alloys

Assessment of the limits of stable passivity of stainless steels is subjective and not amenable to testing by standard methods. Considerably greater information can be obtained on combining weight loss and electrochemical measurements and by recognising that time is an important experimental parameter. This is demonstrated with reference to measurements made on 304L stainless steel in sulphuric acid.

Effect of Potassium Dichromate on the Passivation of Stainless Steel (AISI 321) in Sulphuric Acid

Abstract The effect of potassium dichromate on the passivation of stainless steel in sulphuric acid has been investigated. Tests with K2Cr2O7 up to 4N showed that passivation could be achieved in 3·4 N H2SO4 containing 0·1 N K2Cr2O7, and that the quality of the passivating film increased with the concentration of K2Cr2O7 and with the duration of the passivation treatment. Although passivity could be induced in these conditions at 30°C, at higher passivation temperatures the film quality diminished as shown by long-term decay studies after transfer of the metal to sulphuric acid solutions containing no dichromate. The metal could be passivated in all concentrations of H2SO4. Passivation was also possible in 3·4 N H2SO4 containing 0·2 N K2Cr2O7 and up to 5% NaCl. However, the breakdown of the film produced in the presence of NaCl occurred earlier the higher the concentration of NaCl present during passivation.

Effect of Oxidising Agents on the Passivation of Stainless Steel (AISI 321) in Sulphuric Acid

AbstractThe effect of the nature of oxidising agents on the passivation of stainless steel in sulphuric acid has been investigated, using many kinds of oxidising agents such as K2Cr2O7, KIO4, CuS04, KMn04, H202, HgCI2 and KI03, and the reducing agents FeSO4 and K4Fe(CN)6.All the oxidising agents tested could inhibit the corrosion of AISI 321 type austenitic steel in 3·4N H2S04 to the extent of 89·3–98·7% in short term (1 h) experiments. The potential of the steel was ennobled in the presence of the oxidising agents.The stability of the passivity of steel produced by oxidising agents was determined by measuring the decay in potential of passive steel until its breakdown (—200 mV vs SCE), after its transfer to H2S04 containing no oxidising agent. The quality of the passivating film was also judged by the sensitivity of response (reductlon) to cathodic pulses and to the rate of restoration of potential (self passivation) after interruptlon of the pulse.

Hydrogen evolution reaction on martensitic stainless steel

Following a preceding research on austenitic stainless steel, He hydrogen evolution reaction on martensitic stainless steel in sulphuric acid and in sodium hydroxide solutions was investigated.In acid solutions the electrodes were corrodible and a linear Tafel behaviour was observed only at higher cathodic potentials. The values found for the Tafel slope (120 mV) and for the electrochemical reaction order with respect to the hydrogen ions (0.96), together with some considerations on the coverage of the electrode surface with atomic hydrogen, enabled us to conclude that, as for austenitic stainless steel, the process takes place according to the proton discharge-electrochemical desorption mechanism, the latter being the rate determining step.In alkaline solutions the electrodes were initially covered with an easily reducible oxide film and, contrary to the austenitic stainless steel, it was thus possible to carry out the measurements on an oxide free surface. The values found for the same parameters taken into consideration for acid solutions were 85-90 mV and 0.50.Based on these results the mechanism and the rate determining step were assumed to be the same as in acid solutions, whereas the surface coverage of the electrode with atomic hydrogen was assumed lower, i.e. intermediate.