Showing papers in "British Corrosion Journal in 1986"
417 citations
TL;DR: The free chloride and hydroxyl ion concentrations of the pore electrolyte phase present in mature, hydrated cement pastes containing equivalent quantities of chloride ion, introduced into the mix w...
Abstract: The free chloride and hydroxyl ion concentrations of the pore electrolyte phase present in mature, hydrated cement pastes containing equivalent quantities of chloride ion, introduced into the mix w...
96 citations
TL;DR: In this paper, the short term corrosion behavior of four as-cast commercial aluminium bronzes has been examined by immersing the materials in artificial sea water for various lengths of time.
Abstract: The short term corrosion behaviour of four as-cast commercial aluminium bronzes has been examined by immersing the materials in artificial sea water for various lengths of time. Optical and scanning electron microscopy showed that the phases which underwent selective attack were: martensitiβ in the aluminium bronze, ABI; martensitic β and lamellar eutectoidal fcc α phase in nickel aluminium bronze; the cph y phase present both as a lamellar and matrix constituent in silicon aluminium bronze; and the ordered β phase and the fcc dendritic phase, rich in iron and manganese, in copper manganese aluminium bronze. The rates of corrosion of these phases were influenced by their volume fractions, morphologies, and distributions in the alloys.
70 citations
TL;DR: In this paper, the degradation of ferrous alloys has been studied, and the authors propose a method to identify the source of hydrogen degradation of alloys, including ferrous-alloys.
Abstract: (1986). ‘Hydrogen degradation of ferrous alloys’. British Corrosion Journal: Vol. 21, No. 2, pp. 79-80.
64 citations
TL;DR: In this paper, the influence of alloying elements, particularly of carbon (0·01 and 0·15%), aluminium and chromium (0 and 1·5%), and molybdenum (0, 0·5, and 1.5%), was investigated in the experimental series.
Abstract: High strength low alloy (HSLA) steels, both commercially available and experimentally prepared, were immersed at 45 and 90 m depths in the North Sea for periods ranging from 1·6 to 7·2 years. General corrosion, pitting corrosion, and crevice corrosion behaviour were evaluated after immersion. The influence of alloying elements, particularly of carbon (0·01 and 0·15%), aluminium and chromium (0 and 1·5%), and molybdenum (0, 0·5, and 1·5%), was investigated in the experimental series. It was concluded from the statistical analyses that general corrosion properties are influenced beneficially by aluminium and chromium additions and that pitting resistance is detrimentally influenced by aluminium and molybdenum. The general corrosion rates of the best alloys are afactor of 2–4 lower than those of an unalloyed reference steel similar to steel Fe52. It is also shown that this low general corrosion rate can be combined with a low tendency to pitting corrosion. Notwithstanding the lack of a sound statist...
51 citations
TL;DR: In this paper, an empirical conversion factor was proposed to calculate corrosion rates from the polarization resistance values, in which all time dependent factors were combined, based on the protectiveness of the corrosion product film and hence on the time of exposure.
Abstract: The polarization resistance is often measured to determine the corrosion rate. However, the electrochemical response signal may become distorted by the presence of a corrosion product film on the metal surface. A number of methods have been devised to overcome this difficulty, but these frequently require more sophisticated methods and/or equipment than is available for on-site corrosion monitoring. Contrarily, when the basic linear polarization method is applied, the slow response obtained may necessitate taking measurements under non-steady state conditions, thus introducing an error into the obtained value of the polarization resistance. This error is dependent on the protectiveness of the corrosion product film, and hence on the time of exposure. The same holds for the conversion factor needed to calculate corrosion rates from the polarization resistance values. For such cases it is proposed to introduce an empirical conversion factor in which all time dependent factors are combined.
47 citations
TL;DR: In this paper, a polyamide cured epoxy lacquer and a microporous polycarbonate membrane were examined on a mild steel substrate when immersed in neutral sodium sulphate and sodium chloride solutions, using an ac impedance method.
Abstract: A polyamide cured epoxy lacquer and a microporous polycarbonate membrane were examined on a mild steel substrate when immersed in neutral sodium sulphate and sodium chloride solutions, using an ac impedance method. The process of pore blocking and unblocking is seen to be reflected in changes in the low frequency impedance response.
31 citations
TL;DR: Experience with three methods of using computers to assist in the solution of corrosion problems are described, and each shows considerable promise as a way of making corrosion knowledge available in a form well suited to use in-the solution of practical problenls.
Abstract: Experience with three methods of using computers to assist in the solution of corrosion problems is described. The methods are the use of theoretically based mathematical models, expert systems, and an approach based on a form of decision tree. The strengths and limitations of the nlethods are considered and it is concluded that they are conlplenlentary rather than competitive. Each shows considerable promise as a way of making corrosion knowledge available in a form well suited to use in-the solution of practical problenls, and avoids limitations met with more conventional information handling systems.
18 citations
TL;DR: In this article, the effect of various surface treatments (grinding, polishing, and pickling) and of prefilming (anodizing and passivation) on the susceptibility of aluminium to pitting in 0·5M NaCl solution at 20°C under various hydrostatic pressures has been studied.
Abstract: The effect of various surface treatments (grinding, polishing, and pickling) and of prefilming (anodizing and passivation). On the susceptibility of aluminium to pitting in 0·5M NaCl solution at 20°C under various hydrostatic pressures has been studied. It was found that the susceptibility to pitting increased and that the passivity range (the difference between the corrosion potential and the pitting protection potential) of samples that have not been prefilmed decreased with increasing pressure. Ground and polished specimens are more likely to suffer from localized corrosion, particularly at high pressures. The pitting protection potential remains constant over the entire pressure range for ground and pickled specimens, on which the nucleation and growth of pits take place. Prefilming drastically reduced the susceptibility of aluminium to pitting at both low and high pressures. Passivated specimens showed a higher free corrosion potential than did anodized specimens (the immunity range of alumin...
15 citations
TL;DR: In this paper, the porosity and thickness measurements of various commercially available electroless nickel coatings when subjected to chloride containing waters were analyzed and it was found that porosity increased with exposure to the corrosive environment, thereby allowing galvanically enhanced attack of the steel substrates.
Abstract: Recent experience with electroless (autocatalytic) nickel coatings for the corrosion protection of mining components has been disappointing, particularly in view of their potential for certain applications. This paper presents some laboratory results concerning the corrosion resistance of various commercially available electroless nickel coatings when subjected to chloride containing waters. The laboratory experiments consisted of porosity and thickness measurements, of corrosion tests using a humidity and temperature cycle similar to that found on some coal faces, and of examination by a scanning electron microscope to observe the mechanism of breakdown. It was found that the porosity of the coatings increased with exposure to the corrosive environment, thereby allowing galvanically enhanced attack of the steel substrates. The porosity increase was a result of progressive pitting of the nickel coatings with time and the results supported previous field experience. The various coatings tested exh...
11 citations
TL;DR: These problems are discussed using a model of the relation between ‘information’, in the usual sense, and the ‘knowledge’ needed to address a problem, which helps to clarify the reasons for the problems encountered.
Abstract: The use of computers to handle corrosion knowledge is beginning to attract much attention. Recent experience with a theoretically based mathematical model and an expert system has shown problems in using existing information that had not been anticipated. Both involve representing knowledge in a computer, but in different ways. The attempt to represent knowledge in a computer imposes special requirements, and information which is valid in its original context may not be adequate for the new purpose. Problems of a similar nature have been encountered in developing expert systems in other fields. These problems are discussed using a model of the relation between ‘information’, in the usual sense, and the ‘knowledge’ needed to address a problem, which helps to clarify the reasons for the problems encountered. Two factors are particularly important, the context of the type of problem being addressed and the nature of the software used.
TL;DR: In this paper, the effect of polyox WSR-301 on the rate of cathodic reduction of K3Fe(CN)6 at a pipe wall was determined by measuring the limiting current.
Abstract: To investigate the possibility of using drag reducing polymers as corrosion inhibitors in situations where the rate of corrosion is controlled by the rate of depolarizer diffusion to cathodic sites, the effect of Polyox WSR–301 on the rate of cathodic reduction of K3Fe(CN)6 at a pipe wall was determined by measuring the limiting current. The variables studied were flowrate and polymer concentration. Polyox was found to decrease the rate of depolarizer reduction at the cathode by an amount ranging from 12 to 42%, depending on the Reynolds number Re. The percentage decrease in the rate of depolarizer reduction α was found to be insensitive to polymer concentration and to be related to Re by the equation α = a Re0–5, where a is an experimental constant.
TL;DR: In this article, microstructure was found to have a pronounced influence on the corrosion behavior of CuNi10Fe alloys and the effect of iron content was most pronounced in the alloys containing continuous precipitates.
Abstract: Earlier experiments have shown sea water temperature to exercise a strong. influence on the corrosion behaviour of CuNi10Fe alloys. Investigations attempting to correlate the corrosion product layer properties, and hence the corrosion rate, with microstructural effects are described. Alloy iron content and heat treatment were varied, exposure being carried out at 20 and 40°C under conditions promoting uniform attack. During short term exposure, microstructure was found to have a pronounced influence. On the homogeneous and continuous precipitate containing alloys, good protective corrosion product layers were formed quickly at the higher temperature. The effect of iron content was most pronounced in the alloys containing continuous precipitates. At 20°C, microstructural effects appear to dominate those of iron content. In the long term, however, these effects tended to diminish, all these alloys showing very low corrosion rates under the present test conditions. The discontinuous precipitate conta...
TL;DR: It is concluded that significant savings could be achieved with better methods of predicting behaviour, to help in the assessment of alternative courses of action, and by more effective provision of the information needed to implement the decisions.
Abstract: Recent developments in computing mean that there are now a number of techniques that can be used to make information on corrosion more readily available for the solution of practical problems. The potential benefits are considered, and it is concluded that significant savings could be achieved with better methods of predicting behaviour, to help in the assessment of alternative courses of action, and by more effective provision of the information needed to implement the decisions. The requirements that must be met to achieve these improvements are discussed, and possible computing techniques assessed in relation to them. The methods considered include conventional information handling systems and mathematical models, and the more recent expert systems and decision tree approaches. Many of the conclusions reached are relevant to other aspects of materials engineering as well as to corrosion.
TL;DR: In this paper, the relative concentration profiles of atomic defects across the films have been deduced from studies of the chemical dissolution of anodic oxide films on several valve metals, including tungsten oxide, titanium oxide, and hafnium oxide.
Abstract: From studies of the chemical dissolution of anodic oxide films on several valve metals, the relative concentration profiles of atomic defects across the films have been deduced. Oxides that are characterized by low energies of defect formation contain relatively high concentrations of defects, this concentration increasing as the oxide grows. Films that are characterized by intermediate energies of defect formation contain lower concentrations of defects, which decrease as the oxide grows, while those oxides that are characterized by high energies of defect formation contain low concentrations of defects, which decrease only insignificantly as the oxide grows. Respective examples of each type are tungsten oxide, titanium oxide, and hafnium oxide.
TL;DR: In this paper, the authors describe a test rig for the study of the corrosion of metal specimens under controlled heat fluxes, and discuss the factors influencing the development of crevice corrosion.
Abstract: Novel test rigs are described for the study of the corrosion of metal specimens under controlled heat fluxes. In the corrosion of stainless steels in nitric acid, tests at various heat fluxes with steel surface temperature kept constant have shown that the cooler acid present at the surface under higher heat fluxes leads to slightly smaller corrosion rates than under isothermal conditions. Crevice corrosion can develop under the gasket sealing the stainless steel specimen to the test cell. This crevice corrosion can produce enhanced corrosion rates (by factors up to 100), not only on surfaces within the crevice, but also on those external to the crevice. The factors influencing the development of crevice corrosion are discussed.
TL;DR: In this paper, an investigation of the rusting of steel wire in concrete and mortar is reported, where steel corrosion was monitored using electrode potential measurements, and five experimental parameters were controlled: cement type, mortar porosity, mortar cover thickness, mortar cracking and carbonation thickness.
Abstract: An investigation of the rusting of steel wire in concrete and mortar is reported. Steel corrosion was monitored using electrode potential measurements, and five experimental parameters were controlled: cement type, mortar porosity, mortar cover thickness, mortar cracking, and carbonation thickness. Measurements were made by connecting the reference electrode to three locations on each face of every reinforced mortar parallelepiped sample. The results showed that the mean value of the electrode potential for a sample is correlated with the degree of rusting of the steel, although the location of the measurement does have some effect on the recorded electrode potential. Cracking of the mortar has also been shown to influence the electrode potential.
TL;DR: In this paper, potential-time measurements have been used to study the effectiveness of four wrought heat treatable aluminium alloys and two activated cast alloys in cathodic protection of mild steel.
Abstract: Potential-time measurements have been used to study the effectiveness of four wrought heat treatable aluminium alloys and two activated cast alloys in cathodic protection of mild steel. Only strong bicarbonate concentrations showed serious tendencies to passivate the cast alloys. For the wrought alloys the balance of chloride to sulphate/bicarbonate was critical, but with chloride concentrations of 0·1–3% (as NaCl) certain wrought alloys can be used where commercially pure aluminium is unacceptable.
TL;DR: In this paper, the effect of the progressive replacement of nickel by manganese on the electrochemical corrosion behavior of austenitic spheroidal graphite iron has been investigated in 5% solutions of NaCl, NaOH, and H2SO4 using potentiodynamic polarization and metallographic studies.
Abstract: The effect of the progressive replacementof nickel by manganese on the electrochemical corrosion behaviour of austenitic spheroidal graphite iron has been investigated in 5% solutions of NaCl, NaOH, and H2SO4 using potentiodynamic polarization and metallographic studies. The change in corrosion rate in the substituted alloys depends significantly on the corrosion medium. The results indicate that up to 15%Ni can be effectively replaced by ∼ 8%Mn+2%Cr with relatively small sacrifice of corrosion resistance in 5%NaCl and 5%NaOH media. however, there is a significant loss of corrosion resistance in 5%H2SO4 when manganese is added. The addition of 1,2,3 benzotriazole inhibitor improved the corrosion resistance in the acid medium. The role of microstructure on electrochemical corrosion is discussed using metallographic observations and polarization results.
TL;DR: In this paper, an electrochemical test has been used to evaluate the resistance to crevice corrosion in sea water of some commercial stainless steels, and the results for established alloys correlate well with known service performance, and give confidence in the use of the technique to predict the behaviour of newer materials.
Abstract: An electrochemical test has been used to evaluate the resistance to crevice corrosion in sea water of some commercial stainless steels. The results for established alloys correlate well with known service performance, and give confidence in the use of the technique to predict the behaviour of newer materials. A large variation in resistance to crevice corrosion was found for duplex alloys of the same nominal composition. The differences are thought to be a result of the addition of nitrogen as an alloying element and also the segregation of chromium and molybdenum between the ferritic and austenitic phases.
TL;DR: In this paper, the critical pitting potential of aluminium in 50% ethanediol solution was determined to within 5 m V and it was shown that the Ep value becomes less noble with increase in halide ion concentration.
Abstract: The traditional copper radiators and heaters in automobiles are being replaced by more lightweight versions made of aluminium. Since different halide fluxes are used in the manufacture of the two types of radiator or heater, it is possible for the coolant to be contaminated by more than one halide when the two types of heat exchanger are used in the ·same system. This may give rise to pitting corrosion of the aluminium. Potentiostatic experiments have enab(ed the critical pitting potential of aluminium in 50% ethanediol solution to be determined to within 5 m V and it has been shown that the Ep value becomes less noble with increase in halide ion concentration. The pitting potential of aluminium in solution containing thefluoride ion has bee:nfound to be more noble than expected.
TL;DR: In this article, the authors present a theory and practice of cathodic protection in the British Corrosion Journal: Vol. 21, No. 4, pp. 210-210.
Abstract: (1986). Cathodic protection - theory and practice. British Corrosion Journal: Vol. 21, No. 4, pp. 210-210.
TL;DR: In this article, the role of dimensionless groups in experiments concerned with corrosion in the presence and in the absence of heat transfer is reviewed with specific reference to the design of experiments, the analysis of the data, and the application of data in technical work.
Abstract: The role of dimensionless groups in experiments concerned with corrosion in the presence and in the absence of heat transfer is reviewed with specific reference to the design of experiments, the analysis of the data, and the application of the data in technical work. The derivation of useful dimensionless groups using the method of Similitude is described and demonstrated. The utility of the resulting dimensionless quantities is demonstrated and evaluated by application to available data on corrosion measurements with and without heat transfer.
TL;DR: In this article, a number of duplex stainless steels, whoseferrite content ranged from 25 to 70%, were studied for evidence of corrosion in the aged and welded conditions, and it was found that the best corrosion resistance is obtained from alloys whose microstructures change little with increasing aging temperatures and whose composition is such as to give austenite/ferrite ratios close to 50:50.
Abstract: A number of duplex stainless steels, whoseferrite content ranged from 25 to 70%, were studied for evidence of corrosion in the aged and welded conditions. Microstructural reasons for differences in corrosion properties have been investigated, together with the influence of base alloy con1position. The corrosion performance of duplex stainless steels was tested in highly aggressive media: sulphuric acid andferric chloride solutions. It was found that the best corrosion resistance is obtained from alloys whose microstructures change little with increasing aging temperatures and whose composition is such as to give austenite/ferrite ratios close to 50:50. High chromium contents, which stabilize the passive film, and the addition of nickel and molybdenum have been observed to have a beneficial effect. Selective corrosion was observed in weldments and the heat affected zones of samples with adverse microstructural features. The average corrosion rates calculated from weight loss on as-received, aged, a...
TL;DR: In this paper, mild steel specimens were polarized at 100 mA m−2 for 2 h in a range of inhibitive and corrosive 0·1 M solutions, which had been saturated with oxygen, and hydrogen peroxide was detected only when the solutions were inhibitive.
Abstract: The reduction of oxygen at an iron catbode has been examined previously by Delahay using a polarographic method. He concluded that, owing to overvoltage, hydrogen peroxide could be produced over the potential range −0·2 to −0·6 V(NHE). In the present work mild steel specimens were polarized at 100 mA m−2 for 2 h in a range of inhibitive and corrosive 0·1 M solutions, which had been saturated with oxygen, and hydrogen peroxide was detected only when the solutions were inhibitive. When unpolarized specimens were immersed in solutions saturated with air, hydrogen peroxide was again detected, but in much smaller quantities and again only in the inhibitive solutions. The absence of hydrogen peroxide in corrosive solutions was ascribed to decomposition by anodically formed ferrous salts. Finally, it is established from potential n1easurements that hydrogen peroxide behaves in a similar manner to oxygen in solutions of non-oxidizing inhibitors and it is concluded that cathodicallyformed hydrogen peroxid...
TL;DR: A minor source of lead in food cans exists in the form of small impurity levels in the tin of the coating as discussed by the authors, which explains why some lead pick-up results, previously described as 'anomalous' have been higher than would be predicted from the bulk coating tin/lead ratios.
Abstract: A minor source of lead in food cans exists in the form of small impurity levels in the tin of the coating. The level of this impurity in tinplate currently made by the British Steel Corporation is about 0·03 wt-%. It has been shown, using conventional chemical analysis and electron spectroscopy for chemical analysis, that the lead is not uniformly distributed in the coating. A higher concentration of lead has been found near the tin surface, and it has been shown that the lead migrates in the tin at normal ambient temperatures. This explains why some lead pick-up results, previously described as ‘anomalous’, have been higher than would be predicted from the bulk coating tin/lead ratios. The relative severity of attack on this lead by different products is also shown; most foodstuffs, those based on citric acid, will dissolve only a small amount of it. Only foodstuffs based on malic acid and in cans without an internal lacquer will show a significant tendency to attack the lead. The lead pick-up fi...
TL;DR: In this article, the total thickness loss corrosion rates, together with some chemical and metallurgical test results, were obtained from an examination of two old Redheugh Bridge steel foundation caissons recovered after 89 years' service in a tidal section of the River Tyne.
Abstract: With particular emphasis on underground exposures because of their relevance to steel foundation structures, the total thickness loss corrosion rates, together with some chemical and metallurgical test results, were obtained from an examination of two old Redheugh Bridge steel foundation caissons recovered after 89 years' service in a tidal section of the River Tyne. Below river bed level, the general and pitting corrosion rates were measured to be a maximum of 0·015 and 0·04 mm/year respectively. Above bed level, corrosion was greatest in the low water zone at 0·04 mm/year, but at higher levels the caissons remained variably protected by remnants of a thick tar coating. The corrosion findings are in good agreement with those published for steel pile corrosion. In respect of the measured underground corrosion rates, these, combined with the. generally accepted maximum working stress levels of between 30 and 50% of the yzeld stress, should enable economic steel foundation structures to be designed ...
TL;DR: In this paper, the corrosion of cobalt-nickel alloys at ambient temperatures is reviewed and the growing importance of these alloys in the context of the new generation of metal evaporated tapes and experimental problems in the corrosion study of such tapes are discussed.
Abstract: The corrosion of cobalt-nickel alloys at ambient temperatures is reviewed. In the aqueous phase, data for the anodic and cathodic half-cell reactions are reported, as also for free corrosion. Under most conditions, corrosion resistance increases with nickel content, although in certain circumstances, the 50–50 wt-% alloy is found most resistant. The involvement of catalytically active spinel structured double oxides is apparently important at this composition. Under atmospheric corrosion conditions, such little evidence as exists suggests that cobalt decreases corrosion resistance. The (mainly patent) literature relating to corrosion inhibitors for atmospheric use is reviewed. The growing importance of these alloys in the context of the new generation of METs (metal evaporated tapes) and experimental problems in the corrosion study of such tapes are discussed.