Showing papers in "British Corrosion Journal in 1979"
TL;DR: In this paper, it has been shown that selective phase corrosion can occur near the heat affected zone of welded cast nickel aluminium bronze which is due to the attack of the a phase adjacent to the continuous lamellar K phase.
Abstract: Corrosion trials have been carried out using cast nickel aluminium bronze alloy in the as cast, heat treated and welded states, and the specimens examined using optical and electron optical techniques. It has been shown that selective phase corrosion can occur near the heat affected zone of welded cast nickel aluminium bronze which is due to the attack of the a phase adjacent to the continuous lamellar K phase. Heat treatment of this alloy considerably reduces its susceptibility to corrosion due to both stress relief and structural changes caused by the thermal treatment.
69 citations
TL;DR: In this article, the p-conducting properties of NiO were derived theoretically by taking into account the adsorption of the anions on the oxide film generated the electric field necessary to promote the diffusion of Ni2+ through the oxide, and the rates of oxide thickening in the presenee of different concentrations of different anions were computed and discussed.
Abstract: The variation of the open circutt potential of the Ni electrode in strongly aerated soluiion of different concentrations of Cl−, Br−, I−, NO− 3, SO2− 4 and CrO2− 4 is followdd till steady-stete values are established. In all solutions the steady potentials, Esb, are approached from negative values, denoting film repair and thickening. Except in relatively concentrated Cl− media, no Ni2+ is detected in solution. Plots of the Ni electrode potential, E, as a function of the logarithm of immersion time, t, are linear, satisfying the general relationship:E = al + b1log t ……(1)where a1 and b1 are constants. Equation (1) is derived theoretically by taking into account the p-conducting properties of NiO, and assuming that the adsorption of the anions on the oxide film generates the electric field necessary to promoee the diffusion of Ni2+ through the oxide. The rates of oxide thickening in the presenee of different concentrations of the various anions are computed and discussed. Expressions are deduced r...
57 citations
TL;DR: In this paper, the importance of strain rate in stress corrosion crack growth in some systems implies that distinction between that mode of failure and corrosion fatigue at very low frequencies can be pointless, and there are important consequences here for engineering design approaches to avoiding these modes of failure.
Abstract: Before appropriate preventative measures can be chosen to avoid any corrosion problem the latter needs to be anticipated and predictability possibly poses greater difficulties in relation to stress corrosion than many other modes of corrosion related failure. Consequently some recent work on predicting environmental requirements for stress corrosion cracking is considered, as are the less stringent requirements for corrosion fatigue. The increasing volume of evidence on the importance of strain rate in stress corrosion crack growth in some systems implies that distinction between that mode of failure and corrosion fatigue at very low frequencies can be pointless, and there are important consequences here for engineering design approaches to avoiding these modes of failure. The paper concludes with a discussion of some aspects of the various approaches to preventing environment sensitive fracture.
39 citations
TL;DR: In this article, the inhibitive efficiencies of thiourea and some of its derivatives were studied in relation to the corrosion of aluminium (Grade 1060) in nitric acid at 25°c, 35°c and 45°c.
Abstract: The inhibitive efficiencies of thiourea and some of its derivatives have been studied in relation to the corrosion of aluminium (Grade 1060) in nitric acid at 25°c, 35°c and 45°c. The efficiency in 20% HNO3 at 25°c decreases in the order: p-chlorophenyl thiourea > m-chlorophenyl thiourea ≥ o-chlorophenyl thiourea ≥ phenyl urea > 1:3 di-phenyl thiourea ≥ 1:3 di-p-chlorophenyl thiourea. ≥ 1:3 di-m-chlorophenyl thiourea > thiourea. The adsorption of the compounds is in agreement with Langmuir's adsorption isotherm equation up t a concentration of 250 ppm, at all the three temperatures studied. The percentage efficiencies of the inhibitors were found to increase with increase in temperature from 25° to 45°c. There is no relation between the relative efficiencies of the inhibitors and their critical current densities or primary passivation potentials. All the inhibitors were found to act predominantly on local cathodes although partially effective on the anodes.
33 citations
TL;DR: In this article, the performance of 90/10 copper-nickel-iron alloy in sea water environments is reviewed, covering the effect of iron content and of different heat treatments, behaviour in quiescent sea water and in polluted sea water, resistance to impingement attack (effect of water velocity), crevice corrosion and stress corrosion.
Abstract: Published information on the performance of 90/10 copper-nickel-iron alloy in sea water environments is reviewed, covering the effect of iron content and of different heat treatments, behaviour in quiescent sea water and in polluted sea water, resistance to impingement attack (effect of water velocity), crevice corrosion and stress corrosion. Service performance in condenser and heat exchangers in power stations, ships, etc., in distillation plants and in ships' sea water piping systems is reviewed. The use of the 90/10 alloy for various applications on offshore platforms is then discussed with particular emphasis on sea water piping systems.
26 citations
TL;DR: The corrosion rate of commercial grade, coid-rolled nickel in 50%v/v (5·6 M) hydrochloric acid, with and without the presence of thiourea or one of several of its derivatives, has been studied by gravimetric and electrochemical methods over the temperature range, 23 −79°c.
Abstract: The corrosion rate of commercial grade, coid-rolled nickel in 50%v/v (5·6 M) hydrochloric acid, with and without the presence of thiourea or one of several of its derivatives, has been studied by gravimetric and electrochemical methods over the temperature range, 23–79°c. All the compounds exhibited some ability to inhibit corrosion but, with the exception of sym di-o-tolyl thiourea, they also enhanced corrosion at lower concentrations. The concentration range producing corrosion stimulation increased with increasing temperature and only o-tolyl thiourea and sym di-isopropyl thiourea were capable of maintaining an efficiency of ∼90% inhibition over the full temperature range.For nickel dissolving in uninhibited acid, the Arrhenius relationship was linear and yielded a value of 68·2 ± 3·3 kJ/mol for the activation energy. For acid containing low and medium concentrations of inhibitor. a high proportion of the A rrhenius plots exhibited a change in gradient, reflecting a change in mechanism. Only at...
16 citations
TL;DR: In this article, the growth of thin oxide films (2·0-8·0 nm) on hafnium immersed in aqueous buffer solutions of pH 1-12 has been followed by means of capacitance and potential measurements.
Abstract: The growth of thin oxide films (2·0–8·0 nm) on hafnium immersed in aqueous buffer solutions of pH 1–12 has been followed by means of capacitance and potential measurements. Capacitance measurements show that the corrosion reaction film exerts an action on the behaviour of the metal, in that it determines the magnitude of the open-circuit corrosion potential.In the early stages of oxide film growth, the potential of the hafnium electrode was found to decrease by 59 mV/unit increase in pH, whereas in the final stages the potential decreased by 20–30 mV/unit increase in pH. The reason for the deviation from the 59 mV/unit increase in pH in the final stages of oxide film growth may be connected lvith non-uniform oxygen supply, or with variation of the conducting properties of the oxidefilm with its thickness.
13 citations
TL;DR: In this paper, a model for the variation of potential in a stress corrosion crack is examined using more general boundary conditions, which include the electrochemical reactions at the crack tip, and analytical solutions have been obtained for situations where the potential drop is small.
Abstract: A model due to Doig & Flewitt (‘Mechanisms of Environment Sensitive Cracking of Materials’. 1977.p.113 (London: The Metals Society))for the variation of potential in a stress corrosion crack is examined using more general boundary conditions, which include the electrochemical reactions at the crack tip. Analytic solutions have been obtained for situations where the potential drop is small. Under most conditions of potentiostatic control the potential drop down a crack will be small unless the crack is very long. or unless there is a very large currentflowingfrom the crack tip. Under free corrosion conditions the anodic reactions at the crack tip have to be balanced by cathodic reactions on the surface of the specimen in addition to the cathodic reactions on the sides of the crack.
13 citations
TL;DR: The authors showed that the amount of chromium insoluble in boiling 5M NaOH increases after a short time at raised temperature or after storage, and this effect was shown by ESCA to be due to dehydration of hydroxides.
Abstract: Examination by ESCA of passivation films on tinplate has cast doubt on the assumptions sometimes made that only Cr°; is left after extraction of the films with boiling 5M NaOH, and that the sole action of anodic oxidation in phosphate solution is dissolution of Cr°. Therefore, methods of estimating Cr° content based on these assumptions give results in excess of true values. The amount of chromium insoluble in boiling 5M NaOH increases after a short time at raised temperature or after storage, and this effect was shown by ESCA to be due to dehydration of hydroxides.Application of ESCA to fracture surfaces after detachment of lacquer showed that failure of adhesion occurred between the passivation film and the tin surface and that the growth of tin oxide could introduce a weak layer.
10 citations
TL;DR: In this paper, the pitting corrosion currents reached steady-state values which depended on the type and concentration of both the inhibitive and corrosive anions (Cl−, Br− and I−).
Abstract: The changes with time in the pitting corrosion current density on a steel electrode with the concentration of both the inhibitive anions (CrO42−, HPO42− and WO42−) and aggressive anions (Cl−, Br− and I−) was followed using a simple electrolytic cell. In chromate solutions the pitting corrosion currents started to flow after an induction period, τ, which varied, in one and the same inhibitor solution, with the concentration of the aggressive anion, according to the expression: log τ =a−b log Cagg.The pitting corrosion currents finally reached steady-state values which depended on the type and concentration of both the inhibitive and corrosive anions. At a constant inhibitor concentration,the corrosion current varied with the concentration of the aggressive anion according to: log icorr = al + b1 log Cagg, and with constant aggressive ion concentration according to: log icorr =a2 - b2 log Cinh Comparison was made between the experimentally obtained values of al (a2 and b1 (b2), and the corresponding...
9 citations
TL;DR: Corrosion rates have been measured electrochemically for IN 738 and FSX 414 gas turbine alloys in molten alkali metal sulphates at 1100 K under 1 atm. as discussed by the authors.
Abstract: Corrosion rates have been measured electrochemically for IN 738 and FSX 414 gas turbine alloys in molten alkali metal sulphates at 1100 K under 1 atm. (101 kNm−2) of oxygen and 1·95 × 10−4 atm. (19·8 Nm−2) SO3 for periods of up to 2500 h. Initially protective scale formation, suggested by decreasing corrosion rate, was observed, but this wasfollowed by an increasing corrosion rate associated with failure of the protective scale. Microscopic examination of corroded specimens revealed a sulphide phase beneath the oxide layer penetrating along grain boundaries into the substrate metal.The effect of oxidation reactions, other than the corrosion of the metal, on the determination of the corrosion current has been considered. Under some conditions the corrosion potential approaches the redox potential of the melt and oxidation reactionsfor the molten sulphate contribute significantly to the apparent corrosion current. A correction for this effect is described.
TL;DR: In this paper, the principles of inhibition, the effects of water chemistry on inhibition, types of inhibitors and the application of these to various types of cooling system are discussed and supervision and maintenance of cooling systems and inhibitors are also discussed.
Abstract: The subject of the inhibition of corrosion of cooling water systems is of continuing importance, particularly in view of the increasing demands for more efficient cooling andplant reliability. This report describes the principles of inhibition, the effects of water chemistry on inhibition, types of inhibitors and the application of these to various types of cooling system. The supervision and maintenance of cooling systems and inhibitors are also discussed.
TL;DR: In this paper, a broad review of progress in the science and practice of corrosion and its prevention within Europe in 1977-1978 is presented, based on papers, reports, etc., published in Europe.
Abstract: A broad review is presented, based on papers, reports, etc., published in Europe, on progress in the science and practice of corrosion and its prevention within Europe in 1977–1978. The review considers activities in the member countries of the European Federation of Corrosion, and the topics are classified in broad agreement with the interests of the specialist Working Parties of the Federation. It concludes with an assessment of the functions of these Working Parties and how they might be restructured and extended to take in topics not hitherto covered.
TL;DR: In this paper, the nucleation and growth of transgranular stress corrosion cracks has been studied in Type 316 austenitic steel stressed in MgCl2 solutions of various degrees of acidity and under a narrow range (−0·24 to −0·40 V SCE) of controlled potential.
Abstract: Nucleation and growth of transgranular stress corrosion cracks has been studied in Type 316 austenitic steel stressed in MgCl2 solutions of various degrees of acidity and under a narrow range (−0·24 to −0·40 V SCE) of controlled potential. Slip line attack occurs in relatively acid solutions and is accompanied by the formation of {110} slots which are covered with a chromium rich oxide. In well boiled solutions, which are of low acidity, nucleation occurs at inclusions. MnS particles are efficient crack nuclei, but for other inclusions the size and geometry is of greater importance than chemical composition. High potentials favour pitting and crevice corrosion and such sites are particularly important crack nuclei at low stresses.Edge notched sheet specimens have shown very low threshold stress intensities for crack growth and a sensitivity to prior deformation. Crack tips are extremely narrow and the crack sides show evidence of corrosion. Data pertinent to aslip dissolution model are discussed.
TL;DR: In this paper, the authors reported severe intergranular dissolution of a zinc alloy sacrificial anode operating at above ambient temperature under heat transfer conditions in sea water has been reported.
Abstract: Severe intergranular dissolution of a zinc alloy sacrificial anode operating at above ambient temperature under heat transfer conditions in sea water has been reported. This type of failure has bee...
TL;DR: In this article, a study was conducted on austenitic stainless steel types AISI 304, 310, 316 and 321 to determine their, resistance to cyclic oxidation and to scale spalling and shedding.
Abstract: Studies were made on austenitic stainless steel types AISI 304, 310, 316 and 321, to determine their, resistance to cyclic oxidation and to scale spalling and shedding. Oxidation was carried out in air at 950°c for 30 h each cycle, to a maximum of seven cycles; the specimens after each cyclic oxidation were then rapidly cooled to specified ambient temperatures. Resistance to oxidation as well as to spalling was found to be in the following order: 310 > 316 > 304 > 321. In all cases the separation of initially formed protective scale resulted in the re-formation of less protective scales insubsequent cycles. The re-formed scales exhibited an increasing tendency to cracking and shedding instead of to clean spalling. Internal oxidation, porosity, and stratification in scales increased with the number of cycles, particularly in the 304 and 321 type steels. Grain boundary attack was more evident in 310 and 316 steels. Spalling and shedding of scales was a function of alloy composition, of scale thickn...
TL;DR: The nitro gen-containing steel has an attractive combination of mechanical properties, corrosion resistance, ductility, weldability and castability, and has received application in a wide range of aggressive environments as mentioned in this paper.
Abstract: For the efficient operation of chemical process plant it is of paramount importance to ensure as far as possible that the periods of closurefor maintenance and repair are minimised.The arduous conditions encountered in many chemical plants as a result of progressive trends towards. higher yields, etc., have therefore highlighted the need for greater strength and pitting resistance than can be obtained in conventional austenitic stainless steels. This paper describes the development of ferritic/austenitic high chromium duplex cast stainless steels and demonstrates how, by addition of nitrogen and close control of composition, certain inherent drawbacks of duplex alloys can be overcome. The nitro gen-containing steel has an attractive combination of mechanical properties, corrosion resistance, ductility, weldability and castability, and has received application in a wide range of aggressive environments.
TL;DR: In this article, the authors compared the electrochemical polarisation behavior of titanium in chloride, bromide and iodide electrolytes and predicted that much lower voltages would be required for higher dissolution rates when electrochemical machining is carried out in bromides or iodide solutions.
Abstract: Electrochemical machining of titanium in conventional electrolytes such as chlorideshas some disadvantages since high voltages are required and surface finish can be poor especially in the stray current regions. This paper compares the electrochemical polarisation behaviour of titanium in chloride, bromide and iodide electrolytes and predicts that much lower voltages would be required for higher dissolution rates when electrochemical machining is carried out in bromide or iodide solutions.Observations of surface finish show that bromide electrolytes give much better results than chloride or iodide. Although good surface finish was obtained in bromide solutions, the use of mixtures of chloride and bromide could give even better surfaces,equivalent to bright electropolishing. The mechanism of these phenomena was investigated by electrode polarisation in bromide solutions with. varying pH, ranging from acid to alkali conditions. From this work it was possible to recommend improved electrolytes for th...
TL;DR: In this paper, the life of a solar water heating system will depend on the durability of the materials of construction involved and on the conditions existing within and around the system, and an attempt is made to define the conditions that will affect the performance of materials and also to highlight problem areas.
Abstract: The life of a solar water heating system will depend on the durability of the materials of construction involved and on the conditions existing within and around the system. An attempt is made to define the conditions that will affect the performance of the materials and also to highlight problem areas. Attention is given to water factors, water treatment and the use of inhibitors in the control of corrosion and scaling. Detailed information is given on the performance of various materials, particularly metals, used for constructing solar water heaters.
TL;DR: The influence of rolling direction and tensile stress on the corrosion behavior of a naval carbon steel has been studied by immersing specimens under natural anaerobic conditions in the marine sediments of Genoa Harbour as mentioned in this paper.
Abstract: The influence of rolling direction and tensile stress on the corrosion behaviour of a naval carbon steel has been studied by immersing specimens under natural anaerobic conditions in the marine sediments of Genoa Harbour. The tests were performed on specimens cut both parallel and perpendicular to the rolling direction of ships' plate. Some of the specimens were subjected to tensile stress. Tests lasted 150 weeks, but some specimens were removed after shorter periods of immersion and examined visually and metallographically, and the corrosion products examined by X-ray diffraction.Corrosion was found to be due both to the action of the bacterial H2S of the sediments and of the oxygen present in the outer layers of the sediments. The corrosion rate remained constant until the 90th week of exposure and then showed a marked increase owing to the breakdown of the protective films. The rolling direction affects the transverse surfaces of the specimens and not the surfaces parallel to the rolling plane....
TL;DR: In this paper, the susceptibility of a commercial Zn-Ti alloy to pitting corrosion by Cl−, Br− and I− ions is followed, in oxygen-free NaOH solutions of a concentration which allows the formation of a passivating film on the alloy surface, using the potentiostatic polarisation technique.
Abstract: The susceptibility of a commercial Zn–Ti alloy to pitting corrosion by Cl−, Br− and I− ions isfollowed, in oxygen-free NaOH solutions of a concentration which allows the formation of a passivating film on the alloy surface, using the potentiostatic polarisation technique. Lower concentrations of halide ions have no effect on the dissolution kinetics of the passivating film, while higher concentrations cause the formation of visible pits. Additions of increasing concentrations of chromate, phosphate and carbonate ions cause a shift of the critical pitting potential in the noble direction, accounting for increased resistance to pitting attack. Sufficient concentration of the carbonate ions causes complete inhibition of pitting corrosion. The pitting corrosion potential varies with the concentration of the inhibitive anions, in the presence of a constant concentration of chloride ion, according to S-shaped relationships, from which one can determine the minimum concentrations of the inhibitive ions w...
Abstract: The synergistic effects of sodium benzoate and benzotriazole in inhibiting the corrosion of grey cast iron in 50% ethanediol/water solutions are described. Good inhibition can be obtained in the presence of both inhibitors at concentrations of eachwhich are ineffective when either inhibitor is present alone. The results also showthat the inhibitors are effective on both ‘as-cast’ and machined surfaces. Limited information is presented to demonstrate a similar synergistic effect for the inhibition of corrosion of an aluminium alloy. Some possible adsorption mechanisms to explain these effects are considered briefly.
TL;DR: In this paper, the effect of rolling direction and tensile stress on the corrosion morphology of a naval carbon steel was investigated in continuous immersion tests for a period of about three years in natural sea water in Genoa Harbour.
Abstract: The effect of rolling direction and tensile stress on the corrosion morphology of a naval carbon steel was investigated in continuous immersion tests for a period of about three years in natural sea water in Genoa Harbour. In order to avoid the effects of macrofouling, the specimens were immersed in tanks containing carefully filtered sea water, periodically renewed, and controlled by monitoring the hydrological parameters, oxygen content and temperature.The experiments were performed on specimens cut both parallel and perpendicular to the rolling direction of the plate, and some specimens were subjected to differing degrees of elongation. The corrosion rate was initially high and decreased to reach stable values between the second and third years of exposure. The rolling direction has a greater effect on the behaviour of the transverse surfaces than on the rolling surfaces. In particular, the transverse surfaces which were parallel to the rolling direction underwent considerable localised corrosi...
TL;DR: The determination of the structure of the passivation film on samples of cathodicaly treated tinplate was attempted by transmission electron microscopy as mentioned in this paper, by means of ring diffraction patterns the structure was identified as mainly fine grained polycrystalline SnO2 (tetragonal crystal structure) as well as lower oxides of tin in a continuous film.
Abstract: The determination of the structure of the passivation film on samples of cathodicaly treated tinplate was attempted by transmission electron microscopy.By means of ring diffraction patterns the structure was identified as mainly fine grained polycrystalline SnO2 (tetragonal crystal structure) as well as lower oxides of tin in a continuous film. Single crystal diffraction patterns were recorded, showing evidence for particles of metallic β-Sn, metallic chromium and Cr2O3 (hexagonal crystal structure).
TL;DR: In this paper, the corrosion of mild steel by chlorinated solvents has been investigated and the evidence of acid formation as a result of decomposition of CCl4 and of the corrosive action of the degraded solvent on mild steel has been reported.
Abstract: The corrosion of mild steel by chlorinated solvents has been investigated. The evidence of acid formation as a result of decomposition of CCl4 and of the corrosive action of the degraded solvent on mild steel has been reported. In the presence of water in CCl4 a number of metals produced acid, both when exposed in the liquid or in the vapour, more in the latter case. In general, the catalytic activity of different metals in decomposing CCl4 was in the following decreasing order: mild steel, aluminium, copper, zinc. Nickel, stainless steel and brass did not decompose the solvent. Higher temperatures (> 10°C), longer test periods, a higher water content, the presence of inorganic contaminants and exposure to UV radiation caused more decomposition of CCl4 and greater attack on mild steel. Boiling solvent (containing H2O) or the vapour therefrom prodūced greater corrosion. Hot condensate either flowing past the metal specimens or wetting and drying them alternately produced maximum corrosion.
TL;DR: In this article, a number of methods for the measurement of the corrosion rate of iron have been compared using a natural (unsupported) water and water supported with sodium perchlorate.
Abstract: A number of methods for the measurement of the corrosion rate of iron have been compared using a natural (unsupported) water and water supported with sodium perchlorate. All the methods gave similar results for the supported electrolytes and demonstrated the efficiency off our commercial corrosion inhibitors.Unsupported (dilute) electrolyte solutions could not be investigated by the faradaic impedance method using a simple bridge technique. Polarisation data from the dilute solutions gave misleading results due to the high resistance of the solution and the effect of the diffuse double layer.Sodium perchlorate appears to be a suitable supporting electrolyte for the electrochemical study of iron free from gross films of corrosion product in simple solutions.
TL;DR: In this paper, the potential step method has been used to detect the number of monolayers formed on solid zinc before passivation occurs in dilute sodium hydroxide solutions, and the first peak shows two-dimensional formation of a passivating film with instantaneous nucleation.
Abstract: Previous workers have reported the formation of a monolayer of zinc hydroxide or oxide on zinc amalgam and amalgamated zinc, respectively. In this work the potential step method has been used to detect the number of monolayers formed on solid zinc before passivation occurs in dilute sodium hydroxide solutions. Analysis of the first peak shows two-dimensional formation of a passivating film with instantaneous nucleation. Dependence of the rate constant on hydroxyl ion concentration and potential shows that the rate determining step is the discharge of OH−ions.
TL;DR: In this article, the authors compared different surface conditions produced by pickling, grinding, and mechanical polishing of steels of type 18Cr-2Mo-Ti and AISI 304 and 316.
Abstract: Test specimens of steels of type 18Cr–2Mo–Ti and, as reference materials, AISI 304 and 316, were exposed for 5 years to an urban atmosphere and to a marine atmosphere. All steels were tested in three different surface conditions produced by pickling, grinding and mechanical polishing, respectively. The specimens were examined visually after 1, 3 and 5 years, and by SEM at the end of the tests. It was concluded that: (1) in an urban atmosphere all combinations of steel and surface condition were fully acceptable; (2) in a marine atmosphere the 18Cr–2Mo–Ti steel proved to be slightly better than type 316, which in turn was markedly better than type 304. The polished surfaces were, on average, superior to pickled surfaces, which were in turn slightly better than ground surfaces. Where rust was revealed, it was formed mainly during the first year of exposure. All steels were subject to superficial pitting attack, regardless of surface condition.It was concluded that stainless steel of type 18Cr–2Mo–Ti...
TL;DR: In this paper, the inhibition of aminophenols of the corrosion of Al-4% Cu alloy (B26S) in solutions of sodium hydroxide has been studied in relation to the concentration of alkali and of inhibitor, the period of immersion and temperature.
Abstract: The inhibition by aminophenols of the corrosion of Al–4% Cu alloy (B26S) in solutions of sodium hydroxide has been studied in relation to the concentration of alkali and of inhibitor, the period of immersion and temperature. In general, at constant alkaliconcentration, inhibitor efficiency increases with concentration of inhibitor but, at constant inhibitor concentration, decreases with increase in alkali concentration, the effect being less pronounced with o-aminophenol. The inhibitive efficiency remains almost constant with temperature in the range 20–50°c, but decreases as the period of immersion is increased. At an inhibitor concentration of O·01–2·0% in 0·1 M NaOH the efficiency increases in the order: p-aminophenol < m-aminophenol < phenol < o-aminophenol.The inhibitors appear to function through adsorption following the Freundlich adsorption isotherm. The comparatively better inhibitive efficiency of o-aminophenol appears to be due to chelate formation. From galvanostatic polarisation data ...