Steel In Nitric Acid Solution Research Articles

Electrochemical Behavior and Passive Property of 13Cr Martensitic Stainless Steel in Nitric Acid Solution

Intergranular corrosion behavior of a 13Cr martensitic stainless steel (MSS) in tempered condition was studied. Tempering was done in the temperature range of 300-700 °C after austenitization, and microstructure was established using scanning and transmission electron microscopy. Electrochemical characterizations to establish localized corrosion susceptibility were performed in 5% HNO3 solution. The MSS tempered at 550 °C showed sensitization and significant localized attack during tests in HNO3. Characterization of surface film on this condition revealed an oxide with a higher defect density (through electrochemical impedance spectroscopy–Mott–Schottky analysis) and Fe content (x-ray photoelectron spectroscopy) as compared to that for the austenitized condition. The inability of sensitized MSS tempered at 550 °C to form a protective surface film was attributed to the formation of considerable nano-sized Cr-rich carbide precipitates associated with narrow Cr depletion zones. On the other hand, the MSS tempered at 300 and 700 °C did not show any localized attack in HNO3 and this was attributed to lack of sensitization at 300 °C and de-sensitization at 700 °C.

Effects of Oxidation States of Np on Polarization Curve of Stainless Steel in Boiling 3M-HNO3

It is well known that some certain metal ions in boiling nitric acid cause corrosion acceleration of stainless steel. Neptunium ion from fission products contained in reprocessing solution is known as corrosion accelerator of the stainless steel. Neptunium has several oxidation states (IV, V and VI) in nitric acid solution (up to 3M-HNO3). The metal ions with the REDOX reaction having near the potential of nitric acid promote corrosion of stainless steel but it is not clear why slight amount of the metal ion accelerates corrosion in boiling nitric acid solution. Simultaneous evaluating the coexisting oxidation state Np(IV), Np(V) and Np(VI) and the electrochemical behaviors on stainless steel in nitric acid solution is required in order to understand the corrosion acceleration mechanism. Specially designed electrochemical test cell integrated with optical cell for spectroscopic analysis was developed for this purpose. From results of electrochemical tests, cathode reaction on stainless steel was activated by Np ions. Np(VI) ion made corrosion potential shift nobler than Np(V) and nobler corrosion potential causes accelerating corrosion of stainless steel in nitric acid solution. From results of spectroscopic analysis for oxidation states of Np ion, Np(V) was easily oxidized to Np(VI) in nitric acid solution and Np(VI) was stable state in boiling 3M-HNO3. It was considered that role of Np ions was mediator to accelerate corrosion due to activating cathode reaction and re-oxidizing cycle in boiling 3M-HNO3.

Corrosion Inhibition of Mild Steel in Nitric Acid Media by some Schiff Bases Derived from Anisalidine

Corrosion inhibition performance of mild steel in nitric acid solution containing different concentration of anisalidine derivative Schiff bases viz. N- (4-nitro phenyl) p-anisalidine (SB1), N- (4-chloro phenyl) p-anisalidine (SB2), N- (4-phenyl) p-anisalidine (SB3), N- (4-methoxy phenyl) p-anisalidine (SB4), N- (4-hydroxy phenyl) p-anisalidine (SB5) has been investigated using mass loss, thermometric and potentiostate polarization technique. Inhibition efficiencies of Schiff bases have been evaluated at different acid strength. The inhibition efficiency was found larger than their parent amines. Inhibition efficiencies of synthesized Schiff bases increase with inhibitor concentration. Inhibition efficiency increases up to 98.32% with ansalidine derivative Schiff base.

Aminopyrimidine derivatives as inhibitors for corrosion of 1018 carbon steel in nitric acid solution

The effect of some aminopyrimidine derivatives on the corrosion of 1018 carbon steel in 0.05 M HNO 3 solution was studied using weight loss and polarization techniques. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitor and with decreasing temperature. The addition of KI to aminopyrimidine derivatives enhanced the inhibition efficiency due to synergistic effect. The inhibitors are adsorbed on the steel surface according to Temkin isotherm. Some thermodynamic functions were computed and discussed. It was found that the aminopyrimidine derivatives provide a good protection to steel against pitting corrosion in chloride containing solutions.

Effect of Neptunium Ions on Corrosion of Stainless Steel in Nitric Acid Solution

We have studied corrosion of a stainless steel in nitric acid solution containing neptunium. Using type 304L stainless steel, corrosion tests in boiling neptunium nitrate solution were conducted under immersion and heat-transfer condition. By the weight loss measurement of stainless steel and the quantitative analysis of metallic ions dissolved in solution, the corrosion rates of stainless steel were obtained. The surface morphology was observed by scanning electron microscopy. The corrosion acceleration mechanism was investigated by polarization measurement and spectrophotometry. The corrosion rate of stainless steel was accelerated by addition of neptunium in nitric acid solution. Preferential intergranular corrosion was observed. The corrosion of stainless steel was promoted under heat-transfer condition compared to immersion condition. In polarization measurements, the cathodic over-voltage was decreased; the cathodic current was increased by addition of neptunium. Spectrophotometric measurements showed the oxidization of neptunium in boiling nitric acid. The corrosion mechanism in nitric acid solution containing neptunium suggested the re-oxidation of neptunium.

硝酸水溶液中における304Lおよび316Lステンレス鋼のすきま腐食挙動

硝酸水溶液中における304Lおよび316Lステンレス鋼のすきま腐食挙動

Duplex conversion — alumina coating on stainless steel for high temperature applications

The optimization of conversion coatings on stainless steel in nitric acid solution is obtained using statistical experimental designs. These conversion coatings must present strong interfacial adhesion and must be very porous, in order to allow the deposit and the anchoring of the electrolytic ceramic layer. An electrochemical method was used to estimate the specific area of the coating. The influence of all elaboration factors (temperature, time and bath composition: acid, accelerators, inhibitors) and the interactions between these factors were evaluated, using 2 5−1 and 2 4−1 fractional factorial design. Doehlert uniform shell design was used in order to optimize the conversion coating. The most important factors were nitric acid and thiosulphate concentrations. With such optimized conditions, the real surface area obtained was about 100 m 2 m −2 . This conversion coating modified by ceramic deposits leads to the formation of a coat characterized by strong interfacial adhesion with the steel and by an efficient thermal barrier character. A discussion of the use of experimental designs for the optimization of conversion coating processes is also given.

Semiconducting Behaviour of Stainless Steel Passive Films in Contact with Artificial Seawater

Passive films formed on AISI 316L stainless steel in nitric acid solution and placed in contact with artificial seawater were investigated by Auger analysis, capacitance measurements and photoelectrochemical measurements. The correlation between the electronic structure of the film and the tendency to localised corrosion is discussed, suggesting that the film breakdown involves the ionisation of localised states and/or surface states situated deep in the bandgap.

Corrosion Behavior of Stainless Steel in Nitric Acid Solution under Gamma-ray Irradiation

Influence of the irradiation on the corrosion behavior of stainless steel (type 304ULC) in boiling nitric acid solution was examined by using 60Co γ-ray source. It was found from the experimental results that radiolysis products of nitric acid (NOx, HNO2) resulted from the γ-ray irradiation made the environment in the bulk solution more reducing one. On the other hand, corrosion rate of 304ULC was slightly enhanced by the irradiation, which being trivial from the engineering viewpoint. From the result of an AC impedance measurement, this corrosion enhancement was inferred as caused by an enhancement in the current across the passive film by the γ-ray irradiation on the stainless steel surfaces.

Chemical composition and semiconducting behaviour of stainless steel passive films in contact with artificial seawater

Passive films formed on AISI 316L stainless steel in nitric acid solution and placed in contact with artificial seawater were investigated by Auger and XPS analyses, capacitance measurements and photoelectrochemical measurements. The evolution of the corrosion potential is explained based on the electronic behaviour of the inner and outer layers of the film above and below the flatband potential. The correlation between the electronic structure of the film and the tendency to localised corrosion is also discussed, suggesting that the film breakdown involves the ionization of localized states and/or surface states situated deep in the bandgap.

Corrosion Behavior of Stainless Steel in Nitric Acid Solution under Gamma-ray Irradiation.

Influence of the irradiation on the corrosion behavior of stainless steel (type 304ULC) in boiling nitric acid solution was examined by using 60Co γ-ray source. It was found from the experimental results that radiolysis products of nitric acid (NOx, HNO2) resulted from the γ-ray irradiation made the environment in the bulk solution more reducing one. On the other hand, corrosion rate of 304ULC was slightly enhanced by the irradiation, which being trivial from the engineering viewpoint. From the result of an AC impedance measurement, this corrosion enhancement was inferred as caused by an enhancement in the current across the passive film by the γ-ray irradiation on the stainless steel surfaces.

硝酸溶液中でのステンレス鋼の耐食性に及ぼす共存核分裂生成物の影響

硝酸溶液中でのステンレス鋼の耐食性に及ぼす共存核分裂生成物の影響

硝酸溶液中におけるMo含有オーステナイト系ステンレス鋼の粒界腐食性に及ぼす合金元素の影響

硝酸溶液中におけるMo含有オーステナイト系ステンレス鋼の粒界腐食性に及ぼす合金元素の影響

高酸化性硝酸溶液中における316L鋼の粒界腐食性に及ぼす金属間化合物の粒界析出の影響

高酸化性硝酸溶液中における316L鋼の粒界腐食性に及ぼす金属間化合物の粒界析出の影響

The Role of Silicon in the Corrosion of Stainless Steels in Nitric Acid Solutions

The Role of Silicon in the Corrosion of Stainless Steels in Nitric Acid Solutions

Effects of cold work and galvanic coupling on corrosion of chromium–nickel stainless steels in nitric acid solutions during nitric acid production

Chromium–nickel stainless steels, otherwise chemically resistant, can suffer very high corrosion rates during nitric acid production using Pt–Rh catalyst. The corrosion of these steels is shown to be the result of the establishment of mixed electrode potentials between chromium–nickel steels and Pt–Rh deposits as well as of microgalvanic couples associated with the different potentials of strained and unstrained material in HNO3 electrolyte.

Corrosion and electrochemical behavior of stainless steels under cathode polarization in nitric acid solutions

On stainless steels in nitric acid solutions there is cathode reduction of nitric acid to nitrous acid, which is autocatalyzed by nitrous acid. The nitrous acid is formed in completely, dissociated solutions by the reaction of nitrate ions and hydrogen with the corrosion products (Fe2+ and Cr2+), while in solutions containing homeopolar nitric acid molecules, it is also formed due to reduction of the latter. Cathode liberation of hydrogen on active steels is observed in the region of more negative potentials.

Study of the corrosion and electrochemical behavior of stainless steels during cathodic polarization in nitric acid solutions

1. A study was made of the characteristics of dissolution of stainless steels in nitric acid solutions during cathodic polarization in relation to potential, acid concentration, and temperature. 2. The dissolution of stainless steels during cathodic polarization in nitric acid solutions is retarded by diffusion due to the slowness of the supply of acid to the steel surface.