Steel In Nitrate Solutions Research Articles

Oxidation Features of Low-Carbon Steel in Nitrate Solutions

Oxidation Features of Low-Carbon Steel in Nitrate Solutions

On specific features of oxidation of low-carbon steel in nitrate solutions

On specific features of oxidation of low-carbon steel in nitrate solutions

Two-step oxidation of steel in nitrate solutions

The possibility of increasing the thickness of a magnetite coating (MC) and its heterogeneity due to successive oxidation of low-carbon steel in two bathes based on ammonium nitrate solutions has been shown. Results are shown of a comparative corrosion test of steel with an MC obtained during single- or two-step oxidation in nitrate solutions, with further passivation by the IFKhAN-39U composition, which show the advantages of oxidation in two bathes.

Stress Corrosion Cracking and Localized Corrosion of Carbon Steel in Nitrate Solutions

The stress corrosion cracking (SCC) of carbon steel in nitrate-containing environments has been known for a long time and has become important in managing the integrity of aging underground radioac...

On the possibility of reducing oxidation temperature of low-carbon steel in nitrate solutions

The effect of different additions on the protective properties of a magnetite coating prepared by the oxidation of low-carbon steel in nitrate solution at 70–98°C is studied using physical, electrochemical, and corrosion methods. The introduction of the developed addition URMP-5 to ammonium nitrate solution is shown to yield coatings with good protective properties, not only at 98°C, but also at 70°C. The further treatment of oxidized steel product with passivating compositions creates new fields for their using, even in the presence of direct atmospheric precipitations.

On the Mechanism of Oxide Films Formation on Pearlitic Steels in Nitrate Solutions

During exposing pearlitic steels to nitrate solutions, three mechanisms of iron transfer from the metal phase into solution are observed, depending on the solution pH and the presence of oxidants. The process yields either bivalent iron, colloid-disperse compounds of trivalent iron, or a lepidocrocite deposit. Oxide films thus formed have different protective value. A mechanism explaining the effect of different factors on the protective effectiveness of the oxide films is proposed.

Er+As Ion Implantation to Reduce Stress Corrosion Cracking of Generator Retaining Ring Steel in Nitrate Solution

Abstract It was previously reported that the time to stress corrosion cracking (tf) for generator retaining ring steel (50Mn18Cr4) in a nitrate solution could be prolonged by <6 times using Er+Cr i...

ChemInform Abstract: The Effect of Phosphorus on the Mechanism of Intergranular Stress Corrosion Cracking of Mild Steels in Nitrate Solutions.

AbstractUpon corrosion of Fe‐P alloys (0.003‐2 wt.% P) in hot NH4NO3 solution, P impedes the formation of protective oxide layers on the surface.

The effect of phosphorus on the mechanism of intergranular stress corrosion cracking of mild steels in nitrate solutions

The corrosion behavior of iron-phosphorus alloys with 0.003–2 wt% phosphorus has been studied in nitrate and sulfate solutions. The high P alloys can be considered as a model for grain boundaries with segregated phosphorus. Polarization tests indicated that phosphorus impedes the formation of protective oxide layers on the metal surface in nitrate solutions. According to surface analysis of the corrosion layers by X-ray photo-electron spectroscopy (XPS) it is supposed that upon dissolution phosphorus passes the metal/electrolyte phase boundary in a negatively charged state (corresponding to phosphide) and that the impeding action on the layer formation is due to this state. Constant strain rate tests on mild steels with phosphorus contents in the range 0.003–0.05 P showed a detrimental effect of phosphorus in NH 4NO 3 solution in the potential range −300 mV to −100 mV (NHE). The effect can be correlated to phosphorus segregated at the grain boundaries and can be predicted from the behavior of the Fe-P alloys. However, at potentials −50 mV(NHE) the susceptibility of the steels to intergranular stress corrosion cracking (IGSCC) is even higher and independent of the P content. Mild steels are susceptible to IGSCC even with a very low P content.

Mechanism of Stress-Corrosion Cracking of Mild Steel in Nitrate Solution

Various models for the stress-corrosion cracking (SCC) process in mild steel are reviewed. They can essentially be classified into two main groups: hydrogen-induced SCC and dissolution at the stresscorrosion (SC) crack tip. The first group is excluded on the basis of the present experimental results for SCC of mild steels in nitrate solutions which are consistent with a slip-dissolution process. Susceptibility to intergranular corrosion (IGC) is not a necessary condition for the occurrence of intergranular SCC. Decarburised specimens showed a higher resistance to SCC than decarburised and then nitrided specimens. The experimental results suggest that an excess of nitrogen dissolved at grain boundaries has less influence on susceptibility to intergranular SCC than fine carbide precipitates or an excess of carbon dissolved at grain boundaries.

Certain aspects of the corrosion cracking of steels in nitrate solutions

Certain aspects of the corrosion cracking of steels in nitrate solutions

Intergranular microchemistry and stress corrosion cracking

An important contributory role of grain boundary segregation of residual impurities in the intergranular stress-corrosion cracking of carbon and low alloy steels is proposed. Experimental results are presented of the stress corrosion susceptibility of mild steel in nitrate solution, and in relation to varying grain boundary composition as monitored by Auger electron spectroscopy. The harmfulness of a particular impurity element depends on three factors: its bulk level; its segregation thermodynamics and kinetics resulting in an equilibrium enrichment at the grain boundaries; and its ability to promote electrochemical dissolution of the grain boundary. A hierarchy of impurity elements that exacerbate stress corrosion cracking is presented and correlated with equilibrium oxidation potentials. The results and simple model allow the prediction of the relative harmfulness of impurity elements with respect to intergranular stress corrosion in commercial carbon and low alloy steels from a knowledge of the bulk concentration only. This enables significant improvements in performance to be designed in the alloy by respecifying lower levels of only the one or two highly detrimental impurities.

Role of carbon in corrosion cracking of low-carbon steels in nitrate solutions

Role of carbon in corrosion cracking of low-carbon steels in nitrate solutions

Stress Corrosion Cracking of High and Low Strength Carbon Steels in Nitrate Solutions

Abstract Stress corrosion cracking (SCC) behavior in 60% Ca(NO3)2, 3% NH4NO3 solution boiling at 110 C is reported for relatively pure 1% Ni, 1% Cr, or 1% Ti steels as a function of carbon content. The steels were water-quenched, cold-rolled, or furnace-cooled. Commercial 4140 steel heat-treated to various hardness levels was similarly tested. It was also subjected to SCC in boiling 3% NaNO3 and boiling 3% NaCl. Critical potentials below which SCC does not occur were measured in 3% NaNO3 for the latter steel at 4 hardness levels. The results are interpreted in terms of stress-sorption cracking.

Temperatur- und konzentrationsabhängigkeit der stromausbeute bei der transpassiven auflösung des eisens unter stationären bedingungen

It is possible, to write an expression for the current efficiency of transpassive metal-dissolution reactions, connected with an oxygen evolution, as a function of reaction cd. It can be shown, which parameter of this function is affected by temperature and the concentration of the reactants. The variation of this parameter allows the calculation of the order of the reactions and the activation energies. This introduces a new method for the estimation of kinetic parameters of electrode reactions at high cd, avoiding potential measurements. With respect to the practical importance of a mathematical expression for the current efficiency as a function of cd, concentration of electrolyte and temperature, for instance for the electrochemical machining, the validity of the deduced equations is demonstrated by experimental investigations concerned with the dissolution of steels in nitrate solutions.

Role of oxide films in stress corrosion cracking of mild steel in nitrate solutions

Time to failure of iron with varying carbon content was determined during stress corrosion at 75°C in various nitrate solutions. Ability of these solutions to passivate iron was estimated. It has been suggested that the high rate of the intergranular stress corrosion cracking of mild steel is connected with the formation of the passive γ-Fe 2O 3 film and its sensitivity to the depassivating action of steel constituents such as carbon, segregated at grain boundaries. It is thought that the Fe 3O 4 film also protects the grain boundaries.

Corrosion cracking of low-carbon steel in nitrate solutions

Corrosion cracking of low-carbon steel in nitrate solutions

Role of Corrosion and Stress in the Cracking of Mild Steel in Nitrate Solutions

The effect of precorrosion on the stress corrosion cracking (SCC) of mild steel was investigated in 5 M NH4 NO3 and 2·5 M Ca (NO3)2 at 100°c. Precorrosion reduced the total time to failure by 63 to 86%, indicating that the larger part of the time to failure in SCC tests is associated with corrosion processes which may occur independently of stress. The processes involved intergranular dissolution and increase in potential and pH, resulting in the attainment of electrochemical conditions suitable for passivating film formation on the corroding surface. Estimated rates of crack propagation at the applied stress depended on the actual corrosion potential, as did the maximum current densities on fresh surfaces exposed by abrupt straining.

Role of Corrosion and Stress in the Cracking of Mild Steel in Nitrate Solutions

The effect of precorrosion on the stress corrosion cracking (SCC) of mild steel was investigated in 5 M NH4 NO3 and 2·5 M Ca (NO3)2 at 100°c. Precorrosion reduced the total time to failure by 63 to 86%, indicating that the larger part of the time to failure in SCC tests is associated with corrosion processes which may occur independently of stress. The processes involved intergranular dissolution and increase in potential and pH, resulting in the attainment of electrochemical conditions suitable for passivating film formation on the corroding surface. Estimated rates of crack propagation at the applied stress depended on the actual corrosion potential, as did the maximum current densities on fresh surfaces exposed by abrupt straining.

Action of Carbon in Stress Corrosion Cracking of Mild Steel in Nitrate Solutions

Abstract The effect of total carbon content on susceptibility of iron to stress corrosion cracking (SCC), on the depth of intergranular corrosion without stresses, anodic polarization curves, and the general corrosion rate was examined on decarburized Armco iron and its ferritic or martensitic alloys with carbon up to 1.4% in 5N NH4NO3 and 5N Ca(NO3)2, pH 5.0, at 75 and 100 C (167 and 212 F). The susceptibility to SCC and intergranular corrosion increased with the carbon content increasing up to about 0.009% or above, and it diminished with further increase in the carbon content. Carbon decreased the ability of iron to passivate (depassivating action), but it also promoted deposition of magnetite and enhanced its protective properties (impeding action). It is suggested that the observed effect of carbon on SCC and intergranular corrosion results from the predominance of the depassivating action at low carbon contents, and the predominance of the impeding action at higher carbon contents.