Steel In Acid Research Articles

Inhibiting properties of lignin

Inhibitory efficacy has been determined by the method of the weight losses of steel in acid with native lignin, hydrolysis lignin, ammoniated native lignin, chlorinated hydrolysis lignin, and ammoniated hydrolysis lignin, and without these additives. It has been established that the efficacy of lignin and its modifications as inhibitors of acid corrosion increases with a rise in the number of carboxy groups in the macromolecule, and therefore the ammoniated hydrolysis lignin is the most effective.

Effect of FMI inhibitors on low-cycle corrosion fatigue of steel in acid hydrogen-yielding media

Effect of FMI inhibitors on low-cycle corrosion fatigue of steel in acid hydrogen-yielding media

Hardenability of steels for precision castings

1. The standard medium-carbon steel 45L, widely used for manufacturing cast machine parts, which can be melted in high-frequency induction furnaces with an acid lining, has a high hardenability and tendency to grain growth. 2. Steel 50PPL, which can be melted in high-frequency induction furnaces with a basic lining, has a minimal hardenability. The ideal critical diameter of basic 50PPL is 8.6 mm, and does not increase at quenching temperatures of 800–1050°. Acid steel 50PPL has satisfactory hardenability, with an ideal critical diameter of 14.6 mm in quenching from 800° and 17,6 mm in quenching from 950°. 3. It was found that the fine austenite grain size (grade 12) of basic 50PPL hardly changes with quenching from 800–1000°; for acid 50PPL the austenite grain size increases from grade 12 to grade 11 at these quenching temperatures. 4. Raising the silicon content above 0,3% in acid 50PPL increases the hardenability due to the increasing resistance of austenite to decomposition. 5. Preliminary high-temperature heat treatment (quenching from 1250° and tempering at 650°) of acid 50PPL increases the dispersity of carbide and nitride inclusions and thus reduces the tendency to austenite grain growth, reduces the grain size, and lowers the hardenability. Preliminary heat treatment (quenching from 880° and tempering at 650°) has no effect on the kinetics of austenite grain growth or the hardenability of 50PPL. Hot plastic deformation (forging with cooling in air) increases the hardenability.

The effect of process treatment upon the fatigue strength of heavy carbon steel shafts

1. The fatigue strength of type St 35 acid steel varies very little over the cross section of large shafts. 2. Virtually identical fatigue strengths were obtained on large St 35 shafts. surrounded by sleeves, after normalizing and annealing or after quench-hardening and annealing. 3. Increase in the diameter of the specimens from 12 to 160 mm reduced the endurance limit by 11% (from 12.9 to 11.5 kgf/mm2), regardless of the form of heat treatment of the St 35 steel. 4. Normalizing heavy forgings from St. 35, instead of thermal refining, is an effective process technique: the heat treatment cycle is shortened and there is no need for normally non-available, vertical, quench-hardening, ovens. 5. Surface work-hardening by cold plastic deformation is an effective method of increasing the fatigue strength of carbon steel shafts subjected to a press-fit, and is equally effective after normalizing or after thermal refining.

Triazoles As Inhibitors of Corrosion of Mild Steel In Acids

A study of the inhibition efficiency of triazoles on the corrosion of mild steel in hydrochloric, sulphuric, nitric and phosphoric acids indicates that it is possible to obtain an efficiency of greater than 95% by using benzotriazole of appropriate concentration. At comparative concentrations, the inhibition efficiency obtained with benzotriazole is much greater than that obtained with triazole or amino triazole. The concentration of benzotriazole needed to obtain a high degree of efficiency increases with increase in concentration of acid.Polarisation measurements indicate that benzotriazole increases both the anodic and cathodic polarisation. However, on anodic polarisation, a potential of unpolarisability is observed indicating a change in the kinetics of metal dissolution.Measurements of differential double layer capacity in hydrochloric acid with and without benzotriazole indicate that the surface coverage is complete at a concentration of 2 mM.

Study of the Inhibitive Action of Bakery Waste for Corrosion of Mild Steel in Acid Medium

Bakery waste-egg shell extract was tested for its inhibitory effect towards mild steel in0.5 M H2SO4 solution. The corrosion behavior of the egg shell extract on mild steel (MS)was investigated using weight loss experiments, polarization and impedance measurements.It was found that the egg shell extract has good inhibitive action, showing 97.8% efficiency.Inhibition efficiency increased with increasing concentrations of the egg shell extract.Temperature studies were conducted to evaluate the kinetic and thermodynamic parameters.The corrosion inhibition takes place via monolayer type of adsorption on MS surface.Experimental results are fitted into various adsorption isotherms. Tafel polarization studiesrevealed the mixed mode of inhibition of the egg shell extract. Electrochemical impedanceresults also confirmed the inhibitive nature of the egg shell extract. The results obtainedshowed that the extract of the egg shell could serve as an effective, zero cost,environmentally friendly inhibitor for the corrosion of mild steel in sulphuric acid medium.Keywords: Egg shell, corrosion, inhibition, mild steel, H2SO4 solutionDOI: 10.3126/jncs.v25i0.3282Journal of Nepal Chemical Society Volume 25, 2010 pp 29-36

Effects of Anions on Corrosion Inhibition by Organic Compounds

The effects of inorganic anions, organic compounds, and combinations of the two on corrosion of mild steel in various acids were determined. From corrosion rates of steel in acids the order of the degree of adsorption of anions was concluded to be The largest effects on corrosion mitigation were observed for I− and I− in combination with amines. The specificity of effects attributable to I− suggests a strong interaction with the steel surface possibly through chemisorption. The enhancement of inhibitor efficiency by I− is dependent on molecular structure of the inhibitor. The extent of synergism between I− and organic amines was observed to be in the order: octamethyleneimine> di‐n‐butylamine>n‐octylamine. Synergistic effects of anions and organic cations is greater than can be expected by a shift in the metal surface potential by anion adsorption and must be attributed in part to stabilization of the adsorbed anion layer by organic cations, possibly by covalent bonding.

Effect of Heat Treatment, Composition and Microstructure on Corrosion of 18Cr-8Ni-Ti Stainless Steels in Acids

Abstract Titanium additions to 18Cr-8Ni steels can effectively eliminate susceptibility to intergranular attack associated with the precipitation of chromium carbides. However, these additions also drastically reduce the grain size of these steels and promote the formation of sigma phase. Both of these factors modify the behavior of titanium-stabilized steels in corrosive environments. A detailed investigation of the influence of heat treatment and microstructure on the corrosion resistance of four titanium-stabilized, AISI 321, heats is described. Incomplete stabilization of carbon by titanium leads to precipitation of chromium carbides on heating in the range of 800 F to 1600 F. This type of susceptibility is readily detected in the oxalic acid etch test, the nitric-hydrofluoric acid test, the copper sulfate-sulfuric acid test, the ferric sulfate-sulfuric acid test, and in the nitric acid test. A second type of susceptibility to intergranular attack is associated with the formation of sigma phase, which may precipitate in a sub-microscopic form during heating in the range of 1150 to 1550 F. It is detected only in the nitric acid test and, to a lesser extent, in the ferric sulfate-sulfuric acid test. The action of various acid solutions on titanium-stabilized stainless steels are compared by means of metallographic studies of microstructures and of progressive corrosion, and by measurements of weight loss and change in electrical resistance of corroding specimens. The data obtained are used to explain the action of acids on these steels and to recommend procedures for evaluation testing.

18Cr-8Ni-Tiステンレス鋼の耐酸性に及ぼす熱処理, 化学組成, 顕微鏡組織の影響

18Cr-8Ni-Tiステンレス鋼の耐酸性に及ぼす熱処理, 化学組成, 顕微鏡組織の影響

Effect of Metal Composition and Structure On Corrosion and Oxidation

Abstract Metallurgical factors such as heat treatment and cold-work are not important when corrosion in aqueous media is controlled by diffusion of reactants, e.g. dissolved O2, from the environment. They become important when corrosion control is focused at the metal surface, e.g. steel in acids. In this instance, galvanic cells depend less on where or how metal atoms are placed in their lattice, and more on compositional differences along the metal surface produced by heat treatment or plastic deformation. At elevated temperatures, compositional gradients within a metal are less important. The rate depends instead on diffusion through thick corrosion product layers and on the tendency for spoiling to occur during temperature fluctuations. Metallurgical factors assume greatest importance during initial oxidation, or for thin film formation.

General and Intergranular Corrosion of Austenitic Stainless Steels in Acids: Effect of Cations in the Acids and the lnfluence of Heat Treatment and Grain Size of the Steel

Corrosion of stainless steels by nitric acid is determined largely by the crystallography of grain boundaries. There is preferential attack even on annealed steels. Increasing the rate of dissolution, either by an anodic current or by oxidizing cations, intensifies intergranular penetration. The same crystallographic factors which determine preferential corrosion also determine the precipitation of chromium carbides. Their presence leads to a very great intensification of intergranular attack, as does sigma phase, even as an invisible, pre‐precipitation constituent.Oxidizing cations, such as Cr+6, Ce+4, and Fe+3, increase the corrosion of stainless steels in nitric acid by cathodic depolarization, by shifting the open‐circuit potential of cathodic areas toward more noble values and, probably, by depolarization of anodic areas.The effect of surface finish on corrosion rate is largely a function of the tru (absolute) area produced by various finishes.Ferric ions in ferric sulfate‐sulfuric acid solution greatly inhibit general, or grain‐face, corrosion by anodic polarization. In place of the reduction of hydrogen ions and the evolution of hydrogen gas at cathodic areas, ferric ions are reduced. The consumption of ferric ions is electrochemically equivalent to the weight of steel dissolved. On steels containing intergranularly precipitated chromium carbides, intergranular attack leads to dislodgment of grains and a readily detectable weight loss.Data obtained in sulfuric acid solutions containing ferric nitrate in place of ferric sulfate suggest that it may be possible to develop a 24‐hr evaluation test with this solution.The action of cupric sulfate in copper sulfate‐sulfuric acid solution is similar to that of ferric ions. However, intergranular attack on susceptible steels does not dislodge grains readily, and, therefore, weight loss cannot be used for routine evaluation of the results.Intergranular attack in this solution is greatly accelerated by metallic copper immersed simultaneously with the stainless steel specimen or in contact with it. This acceleration is a result of the formation of cuprous ions and of galvanic action by copper, which is the anode of this couple. The resulting galvanic current and the cuprous ions reduce anodic polarization most readily at grain boundaries containing chromium carbide precipitate and thereby greatly increase the rate of intergranular penetration. Sigma phase does not lead to accelerated intergranular attack in this solution.The influence of grain size on intergranular corrosion depends on the method used for measurement, change in electrical resistance or weight‐loss, and composition of the corroding acid solution.Dissolution of stainless steels in all three acid solutions is predominantly under anodic control. The difference in grain surface corrosion and in intergranular penetration at susceptible boundaries is attributed primarily to a lower anodic polarizability of the metal in such grain boundary zones rather than to any difference which may exist in the open‐circuit potentials of grain surfaces and grain boundaries.

局部電池分極曲線の測定による鉄鋼酸洗の有機抑制剤の作用に関する研究

局部電池分極曲線の測定による鉄鋼酸洗の有機抑制剤の作用に関する研究

鋼の腐蝕に及ぼす歪の影響に就て

The present experiment was carried out for finding the change of solubility of iron and steel in acid, caused by cold-working. The specimens to be tested were previously strained by means of tensile, torsional, impact and compression tests and then they were subjected to the action of one percent sulphuric acid and the loss in weight determined after 72 hours. All the results dealt with in the present experiment led to the conclusion that specimens deformed by stress beyond the elastic limit showed a measurable difference of solubility and the greater the strain, the greater was the corrodibility.