The stress corrosion cracking of welded austenitic stainless steels in MgCl2 solutions in the presence of NaI additions

The influence of Nal additions on the stress corrosion cracking (SCC) of Type 304L and 316L welded stainless steels in 42 wt% aqueous MgCl₂ solution at 154°C has been investigated. The results indicate clearly that addition of 1 N NaI to the boiling MgCl₂ solution prevents SCC of the welded steels. The I⁻ can act as an effective cathodic inhibitor. The correlation between mechanical properties, fracture morphology and the mechanism of the inhibition behaviour of I⁻ on SCC is discussed.     

The assessment of stress corrosion damage in austenitic stainless steel by measurements of cracks formed during constant strain rate and constant load tests in 1M HCl

The penetration of transgranular stress corrosion cracks occurs at a constant rate during uniaxial tensile-type tests, on 304S 12 stainless steel, in 1M HCl, at ambient temperature. Over a range of loads in constant load, and for constant strain rates of 10⁻⁶ s⁻¹ and below, measurements from interrupted tests show a common mode of growth and penetration rate. These results, together with the values of crack initiation periods, may be correlated to quantify and predict stress corrosion damage.     

The stress corrosion cracking of an austenitic stainless steel in HCl + NaCl solutions at room temperature

Stress corrosion cracking (SCC) susceptibility of type AISI 304 austenitic stainless steel was studied in mixed HCl + NaCl solutions at room temperature. Two potential regions of SCC susceptibility were found: one near the open circuit potential, and the other near the pitting potential. The two regions were fused into a single one when the concentration of HCl was reduced. Crack velocities were predicted by the potentiostatic fast strain-rate technique and measured by slow strain-rate tests. A very good correlation was found between the predicted and measured crack velocity values. The cracks were transgranular, and the experimental results showed that an anodic rate controlling step is present in this SCC process.     

Hydrogen embrittlement of stainless steel overlay materials for hydrogenators

An investigation was carried out of the effect of hydrogen absorption on the tensile ductility of composite specimens representing stainless steel weld overlays on low alloy steel substrates as used in the fabrication of hydrogenators. Specimens of the two stainless steels (AISI 309 and 347) involved in hydrogen cracking were also fractured in tension at strain rates between 5.9 × 10⁻⁶ and 1.5 × 10⁻³ s⁻¹ after thermal charging with hydrogen. Results indicated that only the 347 samples suffered significant embrittlement by hydrogen and the original ductility could be restored by subsequent annealing for a time and temperature determined by the hydrogen diffusivity.     

Studies on Stress Corrosion Cracking of Super 304H Austenitic Stainless Steel

Stress corrosion cracking (SCC) is a common mode of failure encountered in boiler components especially in austenitic stainless steel tubes at high temperature and in chloride-rich water environment. Recently, a new type of austenitic stainless steels called Super304H stainless steel, containing 3% copper is being adopted for super critical boiler applications. The SCC behavior of this Super 304H stainless steel has not been widely reported in the literature. Many researchers have studied the SCC behavior of steels as per various standards. Among them, the ASTM standard G36 has been widely used for evaluation of SCC behavior of stainless steels. In this present work, the SCC behavior of austenitic Fe-Cr-Mn-Cu-N stainless steel, subjected to chloride environments at varying strain conditions as per ASTM standard G36 has been studied. The environments employed boiling solution of 45 wt.% of MgCl₂ at 155 °C, for various strain conditions. The study reveals that the crack width increases with increase in strain level in Super 304H stainless steels.     

The effect of temperature on the galvanic corrosion of the copper/AISI 304 pair in LiBr solutions under hydrodynamic conditions

The corrosion behaviour of copper and AISI 304 stainless steel and the galvanic corrosion generated by the copper/AISI 304 pair, have been studied by electrochemical methods. These materials have been tested in an 850 g/L LiBr solution at different temperatures (25-75 °C) and at different Reynolds numbers (1456-5066) in order to study their performance in absorption machines. Results show that copper was always the anodic element of the pair and its corrosion resistance decreases due to the AISI 304 stainless steel galvanic effect. Galvanic corrosion increases with temperature and Reynolds number. However, it was proved that the effect of temperature on galvanic corrosion is more influential than the Reynolds number effect. This fact is also certain for corrosion of uncoupled copper and for corrosion of AISI 304 stainless steel. Experimental values of the corrosion current densities fit well the Arrhenius plot at all the Reynolds numbers analysed and a potential relation between the corrosion current densities and the Reynolds number has been found.     

Electrochemical and corrosion behaviour of work-hardened commercial austenitic stainless steels in acid solutions

This paper describes the results of a study concerning the electrochemical and corrosion behaviour of AISI Types 304L and 316L stainless steels, cold worked under various conditions, in 1M H₂SO₄ and in 0.1M HCl de-aerated solutions. Anisotropic behaviour of specimen surfaces with different orientations to the direction of deformation has been observed. Stress corrosion cracking of the deformed steels can occur at room temperature in the 0.1M HCl solution both in the active and transition regions of the polarization curves.     

Electrochemical and corrosion behaviour of work-hardened commercial austenitic stainless steels in acid solutions

This paper describes the results of a study concerning the electrochemical and corrosion behaviour of AISI Types 304L and 316L stainless steels, cold worked under various conditions, in 1M H₂SO₄ and in 0.1M HCl de-aerated solutions. Anisotropic behaviour of specimen surfaces with different orientations to the direction of deformation has been observed. Stress corrosion cracking of the deformed steels can occur at room temperature in the 0.1M HCl solution both in the active and transition regions of the polarization curves.     

Erosion and Corrosion Behavior of Laser Cladded Stainless Steels with Tungsten Carbide

Laser cladding of tungsten carbide (WC) on stainless steels 13Cr-4Ni and AISI 304 substrates has been performed using high power diode laser. The cladded stainless steels were characterized for microstructural changes, hardness, solid particle erosion resistance and corrosion behavior. Resistance of the clad to solid particle erosion was evaluated using alumina particles according to ASTM G76 and corrosion behavior was studied by employing the anodic polarization and open circuit potential measurement in 3.5% NaCl solution and tap water. The hardness of laser cladded AISI 304 and 13Cr-4Ni stainless steel was increased up to 815 and 725Hv_100?g, respectively. The erosion resistance of the modified surface was improved significantly such that the erosion rate of cladded AISI 304 (at 114?W/mm²) was observed ~0.74?mg/cm²/h as compared to ~1.16 and 0.97?mg/cm²/h for untreated AISI 304 and 13Cr-4Ni, respectively. Laser cladding of both the stainless steels, however, reduced the corrosion resistance in both NaCl and tap water.     

A comparative study of corrosion inhibition of steel and stainless steel in hydrochloric acid by N,N,N′,N′-tetramethyl-p-phenylenediamine

Protection of Metals and Physical Chemistry of Surfaces - The corrosion of mild steel (MS) and AISI type 321 stainless steel (AISI 321) in 1 M HCl solution and the inhibitive mechanism of...     

AE response of type 304 stainless steel during stress corrosion crack propagation

Acoustic emission (AE) signals generated by transgranular stress corrosion cracking (TGSCC) and intergranular stress corrosion cracking (IGSCC) have been compared by means of slow strain rate tensile tests (SSRT) performed using both solubilised and sensitised type AISI 304 stainless steel in a 1 M NaCl + 1 M HCl solution. Results show that the AE activity during the propagation of TGSCC is much higher than the AE activity during the IGSCC propagation. However, no significant difference was found between the mean amplitude and rise-time of the AE signals registered during the propagation of TGSCC and those measured for IGSCC propagation.     

A journey with prasad’s processing maps

The constitutive flow behavior of austenitic stainless steel types AISI 304L, 316L, and 304 in the temperature range of 873 K (600 °C) to 1473 K (1200 °C) and strain-rate range of 0.001 s⁻¹–100 s⁻¹ has been evaluated with a view to establishing processing-microstructure-property relationships during hot working. The technique adopted for the study of constitutive behavior is through establishing processing maps and instability maps, and interpreting them on the basis of dynamic materials model (DMM). The processing maps for 304L have revealed a domain of dynamic recrystallization (DRX) occurring at 1423 K (1150 °C) at 0.1 s⁻¹, which is the optimum condition for hot working of this material. The processing maps of 304 predict DRX domain at 1373 K (1100 °C) and 0.1 s⁻¹. Stainless steel type 316L undergoes DRX at 1523 K (1250 °C) and 0.05 s⁻¹. At 1173 K (900 °C) and 0.001 s⁻¹ this material undergoes dynamic recovery (DRY). In the temperature and strain rate regimes other than DRX and DRY domains, austenitic stainless steels exhibit flow localization. Large-scale experiments using rolling, forging, and extrusion processes were conducted with a view to validating the conclusions arrived at from the processing maps. The “safe” processing regime predicted by processing maps has been further refined using the values of apparent activation energy during deformation. The validity and the merit of this refining procedure have been demonstrated with an example of press forging trials on stainless steel 316L. The usefulness of this approach for manufacturing stainless steel tubes and hot rolled plates has been demonstrated.     

Impact of gamma-ray-pre-irradiation on the efficiency of corrosion inhibition of some novel polymeric surfactants

The effect of gamma-ray-pre-irradiation on the efficiency of two types of polymeric surfactants, (I and II) as corrosion inhibitors for 304 stainless steel in 2 M hydrochloric acid solution was examined. The inhibition efficiency of the undertaken additives was evaluated using both chemical and electrochemical techniques. The chemical structure of the two polymeric surfactants is illustrated as follows: where MA=maleic anhydride; BP=block polymer of polyoxy ethylene-polyoxy propylene (M.Wt=5000 g mol⁻¹).The obtained corrosion data, indicated that the corrosion inhibition efficiency of the inhibitor (II) was obviously not affected by gamma-ray-irradiation, meanwhile the efficiency of the inhibitor (I) demonstrated a remarkable decrease. Scanning electron microscope (SEM) was used to examine the surface morphology of stainless steel samples after immersion in 2 M HCl solution in absence and presence of the inhibitors at concentration of 400 ppm before and after exposure to gamma-ray-radiation up to a total does of 100 kGy.     

An investigation of chloride-substituted Schiff bases as corrosion inhibitors for steel

Polarization and impedance measurements were performed on steel in deaerated 5% HCl solution with and without Schiff base additives within the concentration range 1 × 10⁻⁴–5 × 10⁻³ mol/dm³. The Schiff base compounds used were salicylaldimine, R, N-(2-chlorophenyl)salicyaldimine, 2Cl-R, N-(3-chlorophenyl)salicyaldimine, 3Cl-R, and N-(4-chlorophenyl)salicyaldimine, 4Cl-R. It was found that when the concentration of the inhibitors were increased the inhibitor efficiencies, η, also increased with increasing surface coverage. The results indicated that the ortho-substituted (2Cl-R) compound had the highest inhibition efficiency. All the Schiff base additives studied obeyed the Langmuir isotherm.     

Constant strain-rate testing of AISI type 304 stainless steel in 0.5 M H2SO4 + 0.1 M NaCl solution at room temperature with controlled potential

The constant strain-rate (CSR) test method has been applied to investigate the stress corrosion cracking (SCC) susceptibility of AISI Type 304 stainless steel in 0.5 M H₂SO₄ + 0.1 M NaCl at 25°C within a range of controlled potentials. Cracks were found to form in two distinct potential regions: in the cathodic range, and in the passive potential region. A clear differentiation between the two observed types of cracks was attempted. Crack morphology, the measured current during straining and the reduction of area were used as criteria. SCC was found to occur essentially in the passive potential region; in the cathodic range the cracks were due to hydrogen embrittlement.     

On the corrosion mechanism of AISI 204Cu stainless steel in chlorinated alkaline media

Electrochemical techniques (CV, SECM, CPT) and surface analysis techniques (EDX, SEM) have been employed to assess the corrosion behaviour of the AISI 204Cu stainless steel. The behaviour of this steel has been compared with that of AISI 304 and AISI 434 stainless steels in chlorinated alkaline media. All samples performed well at room temperature under potentiodynamic polarisation up to a chloride to hydroxyl ratio of 10. At this ratio the AISI 204Cu and the AISI 434 steels presented pitting potential at +0.47 V vs. SCE and +0.31 V vs. SCE, respectively. Moreover, the critical pitting temperature was higher for the AISI 204Cu steel than for the AISI 434 steel, respectively 58 °C and 28 °C.In terms of corrosion performance of the AISI 204Cu stainless steel can be classified better than the AISI 434 steel and worse than the AISI 304 steel.Local electrochemical and chemical examinations allowed evidencing the local activity of some pits over long period, and to conclude that the improved corrosion performance of the low nickel alloy AISI 204Cu stainless steel should be ascribed to copper cementation at active corrosion sites.     

Electrochemical Evaluation of Corrosion on Borided and Non-borided Steels Immersed in 1 M HCl Solution

In this study the corrosion resistances of AISI 1018 and AISI 304 borided and non-borided steels were estimated using polarization resistance and electrochemical impedance spectroscopy (EIS) techniques. Boriding of the steel samples was conducted using the powder-pack method at 1223 K with 6 h of exposure. Structural examinations of the surfaces of the borided steels showed the presence of a Fe₂B layer with isolated FeB teeth on the AISI 1018 steel, whereas a compact layer of FeB/Fe₂B was formed on the AISI 304 steel. Polarization resistance and EIS of the borided and non-borided steels surfaces were performed in a corrosive solution of 1 M HCl. The EIS data were analyzed during 43 days of exposure to the acid solution. Impedance curves obtained during this period for the borided and non-borided steels were modeled using equivalent electrical circuits. The results of both electrochemical techniques indicated that boride layers formed at the steel surfaces effectively protect the samples from the corrosive effects of HCl. The main corrosion processes observed on the boride layers were pitting and crevice corrosion.     

Effect of surface polishing on SCC susceptibility of sensitised type 304 stainless steel

Abstract

The effect of surface polishing on the stress corrosion cracking (SCC) susceptibility of sensitised SUS 304 stainless steel was studied by using the well controlled surface polishing method which has been developed for the surface preparation of the semiconductor material. The SCC susceptibility of the polished specimen was examined by using the slow strain rate testing method, at which the specimen was kept at a constant potential in 0·1M Na₂SO₄ solution kept at 368 K. The most effective suppression effect on the SCC susceptibility was found in the case of surface polishing using alumina slurry, followed by water soluble fullerene and diamond slurry, compared with the mechanical polishing with #0/6 paper. Surface roughness and pitting potential of polished surface were compared with the SCC susceptibility of polished sensitised SUS 304 stainless steel. It was found that the SCC susceptibility was decided mainly by the roughness factor rather than pitting resistance. Experimental evidences suggest that the SCC susceptibility was decided by the crack initiation being controlled by surface roughness.     

3.5%NaCl溶液中AISI304不锈钢的电化学行为及有机硅涂层的防护

应用电化学交流阻抗技术(EIS)研究了AISI304不锈钢 在35%NaCl溶液中的电化学行为及表面涂敷有机硅涂料后的电化学行为.结果表明，AISI304不锈钢在在开路电位下的交流阻抗表现为单容抗弧，在浸泡初期，随着时间的延长，耐蚀性提高，当浸泡120?d后，耐蚀性明显下降.不锈钢表面涂敷一层有机硅涂料后，EIS发生了较大变化，浸泡初期为单容抗弧，阻抗值明显增大，浸泡1天后表现为双容抗弧，而不锈钢裸样的始终表现为单容抗弧.     

Stress—corrosion cracking of austenitic stainless steel in hydrochloric acid media at room temperature

Stress—corrosion cracking of solution quenched, type 304, stainless steel can occur at room temperature in HCl solutions ranging between 5·10^?1M and 1M HCl. The cracking observed in HCl solutions is similar to that previously observed in H₂SO₄ + NaCl and HClO₄ + NaCl solutions. Cracking occurs at ? 0·200 V (NHE), in the active potential region, it is under cathodic control, and it develops in conditions under which the corrosion rate of the external surface area is more or less constant and independent of the HCl concentration, in the range 10^?1 M?1 M HCl. At higher HCl concentrations, corrosion rates increase and uneven, general corrosion occurs instead of cracking. The development of pitting and stress—corrosion cracking under active conditions precludes the conclusion that active—passive cells always play a role in localized corrosion and, in particular, in stress—corrosion cracking. Under these conditions, it has been shown that sensitized and non-sensitized specimens behave similarly (giving rise in both cases to transgranular cracking); active—passive cells, due to chromium depletion at the grain boundaries, are not involved. Active—passive corrosion mechanisms can however arise at more noble potentials (0·100?0·200 V NHE), as in the case of HClH₂O₂ solutions of specific concentration, producing intergranular corrosion of the stainless steel in the sensitized condition.