Steel In Phosphoric Acid Research Articles

Inhibiting effect of 2-mercaptopyrimidine on the corrosion of a low carbon steel in phosphoric acid

Polarization and weight loss studies showed that 2-mercaptopyrimidine is effective for the inhibition of low carbon steel over a wide concentration range of aqueous phosphoric acid (H 3PO 4) solutions. The inhibitor retards the anodic and cathodic corrosion reactions with emphasis on the former. The results for uninhibited acid confirm the kinetic expression proposed by Mathur and Vasudevan (Corrosion 38 (1982) 171).

2-Mercaptothiazoline and cetyl pyridinium chloride as inhibitors for the corrosion of a low carbon steel in phosphoric acid

Weight loss studies showed that both 2-mercaptothiazoline and cetyl pyridinium chloride are effective for the inhibition of low carbon steel over a wide concentration range of aqueous phosphoric acid solution. The results for uninhibited acid confirm the kinetic expression proposed by Mathur and Vasudevan (Corrosion 38 (1982) 171).

Corrosion inhibition under heat transfer of 904L stainless steel in phosphoric acid by benzotriazole

The inhibition of the corrosion under heat transfer of the stainless alloy 904L by benzotriazole (BTA), in a phosphoric acid composed by 40% H 3 PO 4+4% H 2 SO 4+300 ppm Cl − has been studied, by using electrochemical and spectroscopic techniques. Results obtained by polarisation measurements show that BTA affects both anodic and cathodic processes. With the increase in concentration of BTA the corrosion rate decreases and the inhibition efficiency increases. The highest inhibitory efficiency is obtained at 10 −1 M in BTA. The inhibitory effect is related to the chemisorption of BTA at the surface of the 904L alloy. Analyses of the surface by SIMS and X-rays confirm this mechanism.

Inhibiting the corrosion of stainless steel in phosphoric acid

The effect of Cu2+ and NO3− ions on the stability of the passive state of a X18H10T type steel in phosphoric acid is investigated by constructing true curves of the anodic and cathodic processes. In a 3 M H3PO4 at 100°C, the steel is found to be in an unstable passive state. Copper(II)- and nitrate-ions transfer it into a steady passive state. Adding copper (II) ions to phosphoric acid accelerates the cathodic process and impedes the anodic dissolution in the active potential range. The steel passivation potential decreases under their action.

Adsorption Studies of the Effect of Thiosemicarbazides on the Corrosion of Steel in Phosphoric Acid

The corrosion inhibition of steel in phosphoric acid by thiosemicarbazide derivatives has been studied using different chemical and electrochemical techniques. The observed order of increasing inhibition efficiency was correlated with changes in the molecular structures of the inhibitors. Potentiodynamic polarization curves indicate that the compounds are mixed-type inhibitors. Electrochemical impedance spectroscopy has been used successfully to evaluate the performance of the inhibitors. AC measurements showed that the dissolution process was activation-controlled. The kinetic–thermodynamic model and the Flory–Huggins adsorption isotherm described the experimental findings well. The number of active sites, binding constant and change in free energy were computed for all the inhibitors studied. It was found that the inhibitor molecule was adsorbed through more than one active centre and occupied more than one active site on the steel surface.

Effect of Thiosemicarbazones on Corrosion of Steel in Phosphoric Acid Produced by Wet Process

Abstract Corrosion inhibition of steel in phosphoric acid (H3PO4) by thiosemicarbazide derivatives was studied using different chemical and electrochemical techniques. Protection efficiency up to 99% was obtained with small amounts (10−4 M) of cinnamaldehyde thiosemicarbazone (CTSCN). The order of increasing inhibition efficiency was correlated with the modification of the molecular structure of the inhibitors. Empirical kinetic relationship was obtained describing the experimental data obtained from the different compounds used in this investigation. Potentiodynamic polarization curves indicated that the compounds acted primarily as mixed-type inhibitors. Electrochemical impedance spectroscopy showed that the charge-transfer resistance increased and the capacitance of the double layer decreased with increasing the concentration of the inhibitor in the medium, confirming adsorption process mechanism. At high concentrations (> 104 M), the capacitance of the double layer leveled off since maximum double-lay...

Passive State Behavior of Special Austenitic and Ferritic Stainless Steels in Phosphoric Acid Polluted by Sulfide Ions

Abstract The passive state behavior of the ferritic Z1 CD 29-4 stainless steel (SS) in industrial phosphoric acid (40 wt% H3PO4 with 1,000 ppm chloride [Cl−] and 330 ppm sulfate [SO42−]) polluted w...

ChemInform Abstract: Polyvinylpyrrolidone and Polyethylenimine as Inhibitors for the Corrosion of a Low Carbon Steel in Phosphoric Acid.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The influence of alloying elements on the corrosion resistance of stainless steels in phosphoric acid medium polluted by sulphide ions

The influence of sulphide ions on the corrosion resistance of some special stainless steels (Z2 CNDU 25-25, Z2 NCDU 25-20, Z2 CNDU 25-6, Z1 CN 25-20, Zl CD 29-4) in 40 wt % H 3PO 4 with 330 ppm SO 4 2− and 1000 ppm Cl − at 80 °C has been investigated using electrochemical (polarisation curves) and spectrometric (SIMS) techniques. The corrosive effect of sulphide ions is confirmed: they increase the anodic current and shift the corrosion potential to more negative values. The presence in the solution of sufficient sulphide ions prevents the establishment of passivity. Critical sulphide ion concentrations above which the alloys Z2 CNDU 25-6, Z2 CNDU 25-25 and Z1 CD 29-4 are no longer able to passivate, are respectively, 1, 5 and 15 ppm S 2−; so, the Z1 CD 29-4 alloy with high chromium content (29% Cr) and without nickel has good behaviour in such polluted phosphoric acid. In the passive state, in order of decreasing dissolution rate, the five steels are ranked as follows: Z1 CN 25-20, Z2 CNDU 25-6, Z2 NCDU 25-20, Z1 CD 29-4 and Z2 CNDU 25-25; sulphur is present in the films probably as sulphides or oxysulphides. Contrary to nickel, the presence of chromium and molybdenum is essential to increase the corrosion resistance of stainless steels in phosphoric acid with sulphides as impurities.

Polyvinylpyrrolidone and polyethylenimine as inhibitors for the corrosion of a low carbon steel in phosphoric acid

Polarization and weight loss studies showed that both polyvinylpyrrolidonc and polyethylenimine are effective for the inhibition of low carbon steel over a wide concentration range of aqueous phosphoric acid (H 3PO 4) solutions. Both polymers retard the anodic and cathodic corrosion reactions with emphasis on the former. The results for uninhibited acid confirm the kinetic expression proposed by Mathur and Vasudevan.

Corrosion Behavior of Stainless Steel in Phosphoric Acid Polluted by Sulfide Ions

Abstract The effect of sulfide (S2−) ions on the corrosion behavior of an austenitic steel (Uranus B6) in phosphoric acid (H3PO4) solutions was examined. The critical concentration at which the effect of S2− ions became perceptible was determined. Aggressive effects of the ions increased with increases in temperature and oxygen content. Results showed S2− ions modified the cathodic and anodic processes.

Influence of sulphide ions on corrosion resistance of special austenitic stainless steels in phosphoric acid

The influence of sulphide ions on the corrosion resistance of some special stainless steels in 40 wt-% H3PO4 with 330 ppm SO2−4 and 1000 ppm Cl− at 80°C has been investigated using electrochemical (polarisation curves) and spectroscopic (infrared, SIMS) techniques. The behaviour of ZI NCDU 25–20 and ZI CNDU 25–25 commonly used in the phosphoric acid industry is compared with that of ZI CN 25–20 to estimate the role of the alloying elements. The corrosive effect of sulphide ions is confirmed: they shift the corrosion potential to more negative values and increase the anodic current in the active and passive states. In order of increasing corrosion rate the three steels are ranked as follows: ZI CNDU 25–25, ZI NCDU 25–20, ZI CN 25–20. The corrosion products consist largely of magnetite in a more or less oxidised state with chromium and nickel substituted for iron. The film formed on the ZI CNDU 25–25 alloy is more protective because of the high chromium content of the mixed oxide and the effect of molybdenum. The film retards the diffusion of corrosive ions through to the metal andfacilitates the development of passivity. However, the presence of a sufficiently high concentration of sulphides in solution prevents the establishment of passivity.

Electrochemical study of corrosion-abrasion of stainless steels in phosphoric acids

The corrosion-abrasion behaviour of several types of stainless steel in phosphoric acid has been studied using electrochemical techniques. The depassivation action of the abrasive was shown to depend on the nature of the material and on the aggressiveness of the medium. In particular, the existence of a synergy between the abrasive and the impurities (chloride and sulphuric acid) in the phosphoric acids was demonstrated. It was found that abrasion enhances localised corrosion. The effect of molybdenum, tungsten, and copper content on the behaviour of stainless steels under corrosion-abrasion conditions was also examined. It appears that molybdenum additions have the most beneficial effect on the corrosion-abrasion resistance of stainless steels in phosphoric acids.

Corrosion inhibition of 304 stainless steel in H3PO4–Cl−solutions by chromium, molybdenum, nitrogen, tungsten, and boron anions: Part 1: Polarisation measurements

Abstract Corrosion inhibition studies of 304 stainless steel in phosphoric acid–chloride solutions with chromium, molybdenum, nitrogen, tungsten, and boron anions have been undertaken. The effect of dichromate, molybdate, tungstate, borate, nitrite, and nitrate ions on the behaviour of the alloy has been studied using potentiodynamic and potentiostatic polarisation techniques. The potentiodynamic results showed that most of these additives improve the corrosion resistance of the alloy. The additives retard both active and pitting attack to an extent depending on the type and concentration of the additive. The potentiostatic (i–t curve) results showed that only nitrite and nitrate salts could achieve complete inhibition of pitting corrosion. The results have been correlated with the beneficial action of the corresponding alloying elements.

Gas Evolution and Pitting in Electropolishing

SummaryThe electropolishing of austenitic stainless steel in phosphoric acid and phosphoric-sulphuric acid mixtures has been studied with special reference to the formation of pits under conditions when gas is being evolved from the surface. These pits can be distinguished from other sorts of etching effect since they are internally polished and thus are superimposed on the polishing process and do not displace it. Electrochemical and physical studies have led to a theory of the relationship between gas evolution and pitting which allows the systematic categorisation of existing and possible methods of counteracting it in practice.

Corrosion resistance of some stainless steels in phosphoric acid

Corrosion resistance of some stainless steels in phosphoric acid

鉄鋼の腐食抑制に関する研究 (第2報)

Corrosion rate of mild steel in phosphoric acid or sulfuric acid were studied using one kind or a mixture of 2 or 3 kinds of nitrogen or sulphur containing organic inhibitors.The results indicate as follows:(1) Inhibiting efficiency of the mixture is excellent compared with the case in which one kind of inhibitor is used.(2) Some inhibitors react as corrosion stimulator when singly used in different kinds of acid, but when they are mixed with one or two other inhibitors they behave as excellent inhibitors.The cause of these phenomena is considered as the formation of compact films of inhibitor molecules, which are polarized by the effect of electric field and great dielectric constant in solution. Such adsorption film becomes compact, when 2 or 3 kinds of inhibitor molecules are adsorbed.