Corrosion products of tin in humid air containing sulfur dioxide and nitrogen dioxide at room temperature

To obtain a fundamental understanding of the corrosion behavior of tin in corrosive gas environments, in situ infrared reflection absorption spectroscopy measurements were carried out on tin in humid air containing SO₂ and NO₂ at room temperature. A series of time-resolved in situ IR spectra in air of 90% relative humidity (RH) containing 10-22 ppm SO₂ suggested that the oxide films on tin specimens had a protective effect and that no significant corrosion occurred. The corrosion products in air of 80-90% RH containing 10-22 ppm NO₂ were SnO₂, SnO, nitrate and hyponitrite. The synergistic effect of SO₂ and NO₂ on corrosion of tin was not observed in humid air (RH of 90%) containing 0.84 ppm SO₂ and 1.8 ppm NO₂.     

Corrosion behaviour in organic acid solutions—I. Tin electrode

The corrosion behaviour of tin in oxalic, citric and tartaric acids in the pH range 2–6 and at concentrations 10^?1–10^?5 M was investigated. The results indicate that increasing the concentration of the organic acid and the pH of the medium up to 4 shifts the corrosion potential to a more negative value and increases the rate of corrosion. At pH values 5 and 6, a shift in the corrosion potential in a noble direction is accompanied by a decrease in the corrosion rate. A linear relationship is observed between the steady state potential (E) and the logarithmic concentration of the organic acid (log C) for the three acids studied:

$\text{E = a ? b}\text{log}\text{C}$

. It was concluded here that the corrosion mechanism in the pH range 2–4 is anodically controlled by the complexing of Sn²⁺ ions with organic acid anions and that the order of decreasing aggressiveness is oxalic > citric > tartaric acids. Corrosion was inhibited at pH values 5 and 6 and this was attributed to film formation on the surface of tin which may result from the hydrolysis of tin complex species.     

Elektrochemische Untersuchungen zum Einfluß von Nitrat und Nitrit auf die Ausgangsruhepotentiale und den Kurzschlußstrom des Elementes Eisen/Zinn in Fruchtsäuren und -säften

Electrochemical investigations into the influence of nitrate and nitrite on the starting rest potentials and the short circuit current of the element iron/tin in fruit acids and juices With the aid of electrochemical measurements the influence is studied of nitrate and nitrite additions on the corrosion behaviour of tin and the iron/tin element in various fruit acids (citric, acetic, tartaric, malic and lactic acids) and vegetable and fruit juices; the results are compared with storage tests conducted in parallel. The electrochemical short time test is generally little suitable for showing the influence of nitrates, in particular because of the slow conversion of nitrate into nitrite which is a corrosion accelerator; the nitrite influence, on the other hand, can be shown quite easily since it produces on the one hand a potential shift toward more positive values and, on the other hand, gives rise to an increase in the short circuit current. These results can be applied to coated cans, too, where the nitrite gives rise to strong dissolution of iron with pitting attack.     

Complex Formation and Corrosion Rate for Tin in Fruit Acids

Abstract

Estimates have been made from electrode potential measurements of the composition and stability constants of the complexes formed by tin with citric, malic, oxalic and tartaric acids in solutions of the concentration range appropriate to canned fruits. The stability constants suggested are highest for oxalic acid, smular to one another for citric and malic acids and a little lower for tartaric acid. Corrosion rates of tin in oxygen-free solutions of the acids fall in the same order as the stability constants, reflecting the influence on the potential of the tin electrode of changes in Sn²⁺ concentration.     

Inhibition of iron corrosion from scratched lacquered tinplate by stannous ions

Abstract

The inhibition of iron corrosion from damaged lacquered tinplate in oxygen free pH 4 citrate buffer solution by the addition of stannous tin has been demonstrated using an accelerated simulated can corrosion test. The inhibition was total for tinplate of nominal coating mass 2·8 g m^?2 for additions of 5–15 ppm of stannous ion, but was only partial for tinplate of nominal coating masses 1·4, 1·0, and 0·5 g m^? up to a 60 ppm addition. The extent of undermining of the lacquer from around a standard scratch was shown to be dependent on the tin coating mass remaining on the tinplate, rather than the presence of stannous ions in solution.     

Dithiocarbamates,Carbon Disulphide and the Corrosion of Tinplate

Abstract

The fungicides TMTD (tetramethylthiuram disulphide) and ziram (zinc dimethyldithiocarbamate) decompose to carbon disulphide and dimethylamine in plain tinplate cans of acid foods. Trace levels of carbon disulphide cause pitting corrosion of the base steel of tinplate with little or no attack on the tin coating. Pitting corrosion differs from the usual form of attack in acid media in which tin is preferentially dissolved and steel is cathodically protected. Carbon disulphide induces pitting corrosion by reducing the hydrogen overvoltage of the tin coating so that cathodic protection of the steel becomes less effective. Carbon disulphide also accelerates anodic corrosion of steel. These effects are of sufficient size to cause inversion of the tin/steel couple potential. Dimethylamine increases hydrogen overpotential of tin slightly but has negligible effect on corrosion.     

Corrosion of Ferrous metals in Batch Cultures of Nitrate-Reducingu Bacteria

Abstract

The corrosion of an iron/carbon alloy has been investigated in short-term experiments in batch cultures of the bacterium Escherichia coli grown in media containing two concentrations of nitrate and in a nitrate-free medium. The growth of the organism was also investigated in the above media but in the absence of metal samples. The results show that growth is affected by the presence of the metal and that the principal cause of corrosion is the formation of metabolic organic acids. The nitrite produced by bacterial reduction of the nitrate reacts with the metal to form a protective film.     

Corrosion of tinplate T54S and T61 in humid atmosphere and saline solution

The initial corrosion mechanism and corrosion behaviors of tinplate T54S and T61 were investigated by chemical stripping layer by layer, humid atmosphere exposure, SEM and potentiodynamic method in saline solutions with the addition of a small amount of components simulating foods and tomato sauce. The results show that T54S initially corroded in the form of pitting at the bottom of grease marks on the surface while T61 displayed the initial corrosion along the steel base on the interface of the tin coating and steel, and both were driven by galvanic corrosion between tin coating as a cathode and base steel as an anode. In the solution of 3.5% NaCl, the free corrosion potential from the outer layer to steel base shifted to negative with an addition of 100 ppm HNO₃ but the potential order reversed as HNO₂ replaced HNO₃ at equivalent content. With an addition of 100 ppm NaHS, a high cathodic peak for either the middle or the inner layers was ascribed to the involvement of the reduction of extra hydrogen, i.e. HS⁻. T54S displayed a wider anodic passive zone and lower passive current density than T61, which resulted from the effect of the alloy layer.     

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

Abstract

The influence of sulphide ions on the corrosion resistance of some special stainless steels in 40 wt-% H₃PO₄ with 330 ppm SO^2?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.     

Papers to be presented at Eurocor '77

Abstract

Despite numerous studies on atmospheric corrosion of copper and copper based alloys, the corrosion induced release processes of individual alloy constituents suffer from significant knowledge gaps. This investigation comprises metal release rate measurements of copper, zinc and tin from some copper based alloys including brass (20 wt-%Zn) and bronze (6 wt-%Sn), and their pure alloying metals, copper, zinc and tin. Data have been generated during a 2·5 year urban field exposure in Stockholm, Sweden and parallel laboratory investigations in a specially designed rain chamber using artificial rain. Brass shows significantly lower annual release rates of both copper and zinc compared to pure metal sheets of its alloy constituents. Zinc is preferentially released compared to copper. Dezincification of brass occurs both at field and laboratory conditions, a process influenced by rain characteristics. Alloying with tin does not largely reduce the release rate of copper from bronze compared to pure copper. No measurable amount of tin is released from the bronze surface.     

Effect of mercury on corrosion in production wells in Gulf of Thailand

Abstract

The effect of mercury on the corrosion of materials used for tubing in oil and gas production wells was studied. Carbon steel (L80) and 13% chromium stainless steel (13Cr) were selected for study by potentiodynamic polarisation. Simulated produced water, with the composition obtained from the Gulf of Thailand field, was used as a corrosive solution. Temperature kinetically increased the corrosion reaction. Chloride ions and carbon dioxide also enhanced the corrosion. Acidity increased the pitting corrosion of 13Cr and increased the corrosion rate of both 13Cr and L80. A concentration of 3–12 ppm of mercury lowered the current density in the passive region and increased the pitting potential of 13Cr. The corrosion rate of L80 was decreased with small amount of mercury addition. The 13Cr showed lower uniform corrosion rate than the L80 in all conditions of the simulated produced water.     

Corrosion protection properties of hydroxamic acid self-assembled monolayer on carbon steel

Self assembled monolayers (SAMs) of hydroxamic acids CH₃(CH₂)_nCONHOH with different alkyl length were formed on the carbon steel electrode surface. The corrosion protection properties of the monolayers were examined and characterized by electrochemical polarization curves, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy (XPS) and contact angle measurements. XPS results showed that the hydroxamic acid molecules adsorbed on the carbon steel surface, and the contact angle values on the modified surface supported the formation of hydrophobic hydroxamic acid SAMs. The results of electrochemical studies showed that the values of the corrosion potential shift towards the positive direction, and anodic currents of the carbon steel dissolution significantly decreases, indicating that hydroxamic acids are anodic inhibitors. However, the chain length and assembling time influence the protection efficiency.     

Corrosion behaviour of bronze in urban environments: influence of tin content

Abstract

In this paper, the influence of the tin content on the corrosion behaviour of copper alloys was investigated. Three different bicomponent bronze alloys were exposed to a natural urban environment. The kinetic corrosion processes and the patina properties were monitored using the open circuit potential, electrochemical impedance spectroscopy and spectrocolorimetry. Results show that the bronze corrosion behaviour improves upon increasing the tin content. In addition, the mechanism of the patina formation is different for the three alloys.     

Influence of alloying elements on electrochemical behaviour of ternary Al-Zn-Ga alloys for sacrificial anodes

Abstract

This work underlines the influence of alloying elements zinc and gallium on the electrochemical behaviour of aluminium alloys used as sacrificial anodes. Both the single and joint effects of these two elements on the free corrosion potential, the corrosion current density, and the development of the passive region were studied. Coupled potential and efficiency measurements were also carried out. It has been shown that the influence of gallium on the extent of the negative shift in corrosion potential of aluminium is greater than that of zinc. As regards the joint influence of the two elements, zinc was found to reduce the extent of the gallium induced negative shift in potential. Finally, for any composition the efficiencies were low, possibly because of partial segregation in these alloys.     

Electrochemical studies of the corrosion of some Cu-Zn alloys in organic acids

The electrochemical corrosion parameters, e.g. corrosion current density, corrosion rate and polarization resistance, of 63Cu-37Zn, 70Cu-30Zn and 58.81Cu-39.53Zn-1.66Pb alloys were measured in aqueous solutions of weak organic acids (oxalic, tartaric and succinic acid). Three techniques were used for these measurements, namely potentiodynamic, Tafel plot and polarization resistance using the model 350A-PARC corrosion measurement system. The effect of acid concentration and temperature on the corrosion parameters of such alloys is discussed.     

Potentialabhängigkeit der Korrosion Mo-freier und Mo-haltiger Stähle in Calciumnitrat-Lösung und Natronlauge

Effect of potential on corrosion of Mo-free and Mo-bearing steels in solutions of calcium nitrate and sodium hydroxide The effect of potential on the corrosion behaviour of three low alloy steels with different carbon and molybdenum contents (0.08 C, 0.01 Mo; 0.08 C, 0.98 Mo; 0.18 C, 1.10 Mo) was investigated in boiling 60 wt.% Ca(NO₃)₂ solution (DIN 50 915) and in boiling concentrated NaOH solutions (20 and 35 wt.% NaOH) by potentiodynamic and chronopotentiostatic polarization measurements (i/E curves) and chronopotentiostatic mass loss measurements (corrosion rate v vs. potential E curves). In Ca(NO₃)₂ solution, i/E measurements give no information about the effect of potential on the anodic dissolution. For the materials investigated, v/E measurements indicate the existence of potential ranges with pronounced differences of the corrosion response. It can be differentiated between active, passive, and transpassive ranges, and also a potential range of secondary passivity was established. Transpassivity and secondary passivity are markedly pronounced with the molybdenum bearing steels but not with the steel free from molybdenum. There are no hints to the occurrence of intergranular attack in the specimens which are free from of internal and external mechanical stresses, whereas such hints could be derived from the shape of the i/E curves. Nevertheless, under mechanical stresses (constant load, CERT conditions) the materials are susceptible to intergranular SCC. The conception that intergranular SCC of low alloy steels in Ca(NO₃)₂ solution is connected with a break-through potential of grain boundary corrosion and hence is to be interpreted as an intergranular attack which, under mechanical stresses, runs in a modified form as SCC with intergranular crack path, cannot be maintained in such general terms. A pronounced active/passive behaviour is observed in NaOH. The effect of potential on anodic metal dissolution which is derived from v/E curve is also established by i/E measurements. For molybdenum bearing steels, the active potential range is somewhat extended to more positive potentials. Manifestations of localized attack, e.g., intergranular corrosion, do not occur. From the investigations, no hints to the cause of the deterioration of the resistance to intergranular SCC in caustic solutions by molybdenum can be derived.     

Influence of Movement and Temperature on the Corrosion of Mild Steel IV. Inhibition by sodium metaphosphate glass

Abstract

A study has been made of the influence of small additions of sodium metaphosphate glass (a sodium polyphosphate) on the corrosion of mild steel in a solution of 25 ppm sodium chloride at flow velocities of 1·2, 20 and 200 cm/sec. The inhibitor efficiency is found to depend on the concentration, the rate of flow and the presence of small concentrations of calcium ion. Small additions of metaphosphate glass can actually stimulate corrosion of mild steel at low flow velocities in the absence of calcium although in the presence of cqlcium they have a small but beneficial effect. The efficiency of inhibition increases with increase in flow velocity.

The inhibition is produced by a visible film largely of a colloidal nature the amount of product becoming smaller when the corrosion rate is lowered. Potential measurements have shown that polyphosphate acts mainly as an anodic inhibitor in the absence of calcium and as a cathodic inhibitor in its presence. Stimulation can occur owing to the complexing power of metaphosphate glass and its depolarising action at the anode.     

Influence of tin addition on corrosion resistance of aluminium ion platings

Abstract

Aluminium ion platings are galvanically compatible with the aluminium alloys used in the aircraft industry and prevent galvanic attack when in contact with them. However, these platings fail to provide the good lubricity which the traditional, but toxic, cadmium platings are known to provide. Adding tin to aluminium ion platings can improve their frictional characteristics. In this work, electrochemical polarisation and metallurgical studies have been used to examine the influence qf introducing 5%Sn into aluminium ion platings on their corrosion resistance. Results have shown an increase in the corrosion tendency as indicated by a shift of the corrosion potential in the active direction and an increase in the corrosion current density which can be related to a galvanic action between two different phases of aluminium rich columnar grains. Domes observed within these grains can easily be removed during early stages of corrosion leaving cavities in the platings, thus providing another possibility of galvanic attack between the plating and substrate taking place.     

The influence of tin and silver as microstructure modifiers on the corrosion rate of Pb–Ca alloys in sulfuric acid solutions

The effect of microstructure modifiers, Sn and Ag, on the corrosion rate of commercial Pb–Ca alloy in H₂SO₄ electrolyte was investigated by the potentiodynamic polarization and by the weight loss corrosion rate measurement at the open circuit potential. The effect of microstructure modification of the Pb–Ca alloy, provoked by the alloying with tin and silver as well as by the proper thermo‐mechanical treatment, is recorded by optical microscopy. The weight loss experiments have shown three‐ to five‐fold decreases in the corrosion rate of ternary Pb–Ca–Sn and quaternary Pb–Ca–Sn–Ag alloys, compared to the results for primary Pb–Ca alloy. It is largely in accordance with the results of potentiodynamic polarization measurements that showed comparable decrease in the passive current density of the modified alloys. The obtained results are discussed in terms of the synergetic effect of the addition of modifiers and the thermo‐mechanical treatment on to the Pb–Ca alloy microstructure refinement, and accordingly the increase in their corrosion resistance.     

Corrosion of copper in 3% NaCl solution polluted by sulphide ions

The effect of sulphide addition on the corrosion of copper in 3% NaCl was studied. The concentration of sulphide was kept rather low, up to 10 ppm. The effect of sulphide on the copper corrosion is controversial in the literature, and worth to verify by means of various experimental techniques. The polarisation curves, plotted from a potential close to the open circuit one to negative or to positive direction indicated a decrease of corrosion current density, whereas a quartz crystal microbalance indicated an acceleration of corrosion rate with increasing sulphide ion concentration. The reduction of corrosion product in boric-borate buffer solution allowed establishing that the thickness of corrosion product increased slightly when the sulphide concentration is higher. The EIS measurements showed a slight increase of corrosion rate by addition of sulphide ions, in agreement with EQCM experiments.