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By Sarah Belair, Gauthier Deblonde, Valerie Weigel, Alexandre Chagnes, Gerard Cote

"Niobium and tantalum are strategic metals for electronic and alloys industries. They are produced by pyrometallurgy and hydrometallurgy but most of the niobium and tantalum production processes are not environmentally friendly. For instance, in the hydrometallurgical route, niobium and tantalum separation can only be achieved by liquid-liquid extraction in the presence of hydrofluoric acid by taking advantage of the difference in niobium(V) and tantalum(V) speciation in fluoride-based media. Therefore, the environmental footprint of hydrometallurgical processes for the production of niobium and tantalum could be clearly lowered by replacing HF or NH4F by greener media such as alkaline solutions in which high solubility of niobium(V) and tantalum(V) can be achieved.The development of such new efficient and environmentally friendly hydrometallurgical processes requires a fine description of the physicochemistry of niobium(V) and tantalum(V) in alkaline solutions. Unfortunately, literature data show a huge discrepancy on niobium(V) and tantalum(V) speciation in such media. This paper gives a brief overview of the niobium(V)-tantalum(V) production processes and paves the way to the development of alternative processes in alkaline media by presenting and discussing recent advances in the physicochemistry of niobium(V) and tantalum(V) in these media.INTRODUCTIONNiobium and tantalum are strategic metals since they are used for the production of alloys and super alloys, capacitors and magnets in strategic industries such as electronic, aeronautics and automobile. The main sources of niobium and tantalum are given in Table 1."

Jan 1, 2016

By J. S. Scott

"The Quemont property comprises 640 acres lying directly north of and adjoining the Noranda (Horne) mine. During 1926 to 1928, United Verde Extension Mining Corporation sank a shaft 235 feet and did 3,000 feet of development work on the 215-foot level. Between 1929 and 1930, Quemonr Mining Corporation deepened the shaft to 926 feet, and did further lateral work and drilling on the 500- and 900-foot levels. This work was confined to an area close to the south boundary and met with little encouragement.Following a period of idleness a magnetic survey was made in the winter of 1944, followed in the summer of the same year by some 6,000 feet of drilling. The first successful hole was drilled in February, 1945, from the ice of Osisko lake.To the time of writing, 131,000 feet of drilling, surface and underground,have indicated a large tonnage of gold-silver-copper-zinc ore, and although some knowledge of the geology and structure is emerging, it is too early to draw definite conclusions. The following brief description deals only with those structural features that are reasonably well indicated."

Jan 1, 1954

By X. F. Liu, O. Buzzi, Y. Sieffert

This study falls in the context of underground coal fires (UCF) where burning coal can elevate the temperature of a rock mass in excess of thousand degrees. The objective of the research was to experimentally investigate the change in mechanical behavior of a rock when subjected to temperatures up to 900 °C. Several blocks of an Australian mudstone were collected from a mining site in New South Wales, Australia. X-ray diffraction and thermal-gravimetric analysis were conducted on powdered rock in order to determine the critical temperatures at which the main mineralogical changes occur. Then, cylindrical specimens were prepared from intact rock blocks for unconfined compression tests. These rock specimens were then treated by heating in a temperature-controlled furnace at temperatures varying from 100 °C to 900 °C. The heating process consisted of two stages: raising temperature with very slow rate of 1 °C per hour followed by a holding period of 24 hours and then a slow cooling process to room temperature. The compression tests were carried out on treated rock specimens to characterize the change in compressive strength. The macroscopical study was complemented by microstructural investigations via optical microscope, scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). Results show that the unconfined compressive strength of mudstone decreases with increasing heating temperature up to 450 °C, beyond which it increases. This can be explained by the combined effects of micro cracks and mineral thermal reactions caused by heating process.

Jan 1, 2015

By W. F. Scott, K. L. Somerville

"This paper outlines the development and inplementation of functional training at the Thompson Mine of Inco Metals Company, Manitoba Division. This training is an extension of similar methods implemented throughout the company to meet safety and health and productivity objectives. It consists of the orientation to the mine, induction in the basic mining skills, and specific training in drilling and other skills in the mine. Initial results indicated a positive effect on the safety performance and proficiency of the mine workforce.IntroductionThe primary mining method at the Thompson Mine is mechanized cut and fill, with secondary recovery of pillars by undercut and fill . These methods require a workforce of about 900 hourly operating employees to obtain capacity production of 6500 tons of ore per day.Historically, turnover of mine employees has been high and large numbers of new recruits are introduced to the mine every year. These men are recruited primarily in Manitoba, but also from distant areas of Canada; most of the se people have no previous mining experience.Training has always been an important component of mine operations. Mine supervisors and experienced miners have committed an appreciable amount of time and effort to training these new recruits. As well, training efforts have been directed toward upgrading the skills of experienced workers.Recently, a growing awareness of the significance of this training effort and its impact on accident frequency, productivity, turnover and other important parameters of the mine operation has led to a review of training methods. The training program described in this paper has resulted from this review."

Jan 1, 1981

By Michael Chender

Emerging Equity Sources ? Larger IPOs ? China Inc. ? Other sovereign wealth funds ? New funds and higher allocations ? Private equity

May 1, 2010

By Francisco Tamargo

"This paper refers to a new process for the full recovery (above 98%) of zinc and other valuable metals (Pb, Ag, Au) accompanying zinc in its concentrates while iron is separated as a marketable product free of any harmful impurities and suitable for sale to the cement industry. The process has been especially designed to achieve the following goals: maximizing the recovery of zinc and those valuable metals that are present in most zinc concentrates (lead, silver, gold); allowing the recovery of other valuable metals such as indium or germanium that could be present in some zinc concentrates; avoiding or minimizing the need for residue disposal in safe areas as it is the common practice nowadays in the zinc industry. Finally, the process achieves the previously related goals at a competitive cost, in line with the existing more efficient operations while using conventional equipment working under atmospheric conditions. The new process can be easily implemented in those smelters using the jarosite or goethite processes as well as in those smelters using direct leaching as a part of the processing facilities. A study has already been conducted on the use of jarosite in the cement manufacturing process, in the raw mix preparation as well as for a set controller. It shows that use of clean jarosite in the manufacture of ordinary Portland cement can result in improved quality of the clinker. Jarosite showed compatibility to influence the burning characteristics of the cement raw mixes. The presence of SO3 bearing mineral phases such as natrojarosite showed the suitability of clean jarosite for use as a set controller in cement production.INTRODUCTION Iron is by far the most abundant impurity accompanying zinc in its concentrates, and consequently, iron residue disposal is a major environmental concern for many zinc smelters in the world. This is especially true during the last 30 years when environmental restrictions became more and more strict. Much research work has been carried out during the last 30 years to try to find a solution for this important issue, but with little success. Only the jarofix process represents a partial solution to this problem as jarofix is stored nearby the smelters with certain limitations as a non-contaminant residue. However, it does not avoid the need to dispose of an important amount of residues every year, representing an environmental liability. Meanwhile, the number of countries limiting or banning the disposal of iron residues generated by the zinc smelters is growing, so that the solution to this problem is becoming an urgent matter right now. At the same time, the lack of appropriate available land for iron disposal is also a major concern in many cases."

Jan 1, 2016

By Andrew Thrift

Overview ? Problem ? Research question ? Literature review ? Methodology ? Results ? Discussion and recommendations ? New developments Problem ? Increasingly higher expectations ? Inadequate consultation leads to conflict rather than collaboration ? Consultation practice is often weak on decision-making ? Influence of consultation on planning is Unclear Research question ? Are Structured Decision Processes (based on decision analysis) an effective methodology for involving stakeholders in consultative decisionmaking in the mining industry?

May 1, 2006

By T. Boiselle, C. Gielen, P. Henry, J. M. Bier

"Hydrometal is specialized in the production of zinc sulphate from complex secondary raw materials. Electric Arc Furnace (EAF) dust is one of the more interesting potential sources to produce zinc sulphate. In order to minimize waste quantities generated from EAF dust treatment, our R&D team has developed and patented a new process to recover the Fe contained in the dust as iron oxide product to be used and sold into the pigment market. The process is based on a specific reductive leaching step of the zinc ferrite contained in EAF dust, followed by a purification step to remove impurities (Ni, Cr, Cu...) and finally the controlled precipitation of the iron oxide. The aim of the iron precipitation step is to obtain the right shape and length of crystals in order to guarantee the right color and tinting strength of the pigment. The innovative aspects of the process results in the controlled oxidation of the iron to get the right crystal size and good purity material. The iron product can be valorized as red or yellow pigment often produced by the Penniman-Zoph process.INTRODUCTION A Few Words about HYDROMETAL Hydrometal SA (Engis, Belgium) is a subsidiary of Jean Goldschmidt International SA (JGI) in Brussels. JGI is mainly involved in metal trading activities (Goldschmidt, 1995). In 1985, JGI acquired the leaching circuit of a Belgian electrolytic zinc producer located in Engis, a few kilometers south of Liège, near the river Meuse and it was decided to name this plant: SA HYDROMETAL. Hydrometal is well connected by water, rail and road from its central location in the industrial region of Liege, in the heart of Europe. The company received in 1997 an additional license to process and recycle toxic and hazardous waste. Figure 1 shows a picture of the plant."

Jan 1, 2016

By W. J. Kuit

"Complex facilities which provide for the collection, management and treatment of effluents emanating from the Sullivan mine and concentrator tailings were made operational in October, 1979. Key features of the system are the use of upgraded tailings ponds for the storage of up to 800 million litres of metals-contaminated effluents, a treatment plant employing lime in a high density sludge process and a sludge-impoundment facility designed for maximum long-term environmental safety. The completed works are cap1ble of satisfying a difficult range of operating requirements imposed by highly variable weather conditions, drainage flows and soluble metals loadi11gs. Final capital expenditures for the project will approach $10 million and annual operating costs are estimated at $0.8 million.This paper discusses the Kimberley effluents treatment project and the major considerations in its development. The treatment process, major plant equipment and initial operating experience are also described."

Jan 1, 1980

By Robert B. Parsons

"Income tax legislation is not keeping pace with federal and provincial environmental legislation. There is a vast array of new environmental regulations at various stages of implementation across the country. Unfortunately, there are serious concerns about the deductibility of significant payments which mining companies will be required to make under these new rules, and the Department of Finance seems to be reluctant to act on these concerns. IntroductionWhile the federal and provincial governments are racing ahead with obvious fervour to introduce new envirorunental laws, the tax rules relating to envirorunental costs are being allowed to lag far behind. In a nutshell, the tax treatment of envirorunental costs is not keeping pace with the new envirorunental legislation.One of the most serious concerns of the mining industry is the deductibility of mine reclamation or closing costs. The producing provinces are well advanced down the road toward mandating upfront deposits, bonds, or similar financial guarantees to protect the envirorunent from the operation and eventual closure of a mine. These requirements are not small. In some instances, they can amount to tens of millions of dollars. And, if there is no tax deduction for these sums when they are set aside by the mining company, then the costs have to be paid out of the company's after-tax earnings."

Jan 1, 1991

By Edward Rybinski, Serkan Dikmen, Walter Valery, Jorge Ghersi, Roberto Valle, Alex Jankovic, Javier Linares, Frank Davila

Compañía Minera Antamina is a polymetallic mining complex that produces copper and zinc concentrates as primary products and molybdenum and lead/bismuth/silver concentrates as by-products. In 2007, Metso Process Technology and Innovation (PTI) was contracted to increase SAG mill throughput by integrating and optimising blast fragmentation, crushing and grinding for the harder M4/M4A (CuZn) ores. Following the implementation of recommendations provided by Metso PTI, the SAG mill throughput increased from 2750tph to reach an average of 3600tph for the remainder of 2007. Due to continued application of mine to mill integration and optimisation philosophy, by 2010, the concentrator consistently exceeded the target of 4400tph while processing harder CuZn ores.

Jan 1, 2012

By J. Kuipers, R. W. Lawrence, P. B. Marchant, W. Brooks, J. T. Chapman

"Bioleach testing and piloting was conducted on refractory gold sulphide concentrate from Austin Gold Venture in Nevada during 1988. The objective of the test programme was to determine the technical and commercial viability of bioleaching as a concentrate pretreatment step prior to gold extraction by cyanidation. Baseline CIL cyanidation typically resulted in < 20% gold extraction from the Austin concentrate. Bioleaching enhanced gold extraction up to 95% using conventional CIL techniques. This paper summarizes the bioleach test programme and results, including pilot plant studies onsite, and describes the commercial design details for a possible retrofit of the Austin flotation tailings leach circuit to accommodate 20 tpd and 40 tpd capacity concentrate bioleach facilities.INTRODUCTIONBioleach testing on a refractory carbonaceous sulphide concentrate from Austin Gold Venture (AGV), was initiated in late 1987 as part of an ongoing programme at Austin to investigate alternatives to concentrate smelting. Preliminary batch biooxidation tests at Coastech indicated that over 90% gold extraction by carbon-in-leach (CIL) cyanidation of the bioleach residue could be achieved, compared with less than 20% gold extraction on untreated concentrate by similar CIL processing.Subsequently, a more rigorous laboratory study was undertaken at Coastech to establish continuous biooxidation operating criteria on a bench scale. The objective of continuous testing in the laboratory was to provide confirmation of enhanced CIL response based on continuous bioleach products and to determine key process operating and design parameters for pilot testing. The success of the laboratory test program led to the installation of a mobile pilot plant at Austin Gold Venture. The plant was operated by Coastech and AGV during 1988 to provide scaleup data and design criteria for commercial design and feasibility analysis. Based on pilot plant operating data, a detailed commercial bioleach plant was designed as a possible retrofit to the existing 1000 tpd CIL plant. Capital and operating costs were estimated to provide a commercial feasibility study of bioleaching as an oxidative pretreatment for Austin refractory concentrate."

Jan 1, 1989

By S. M. Bulatovic, D. M. Wyslouzil

"This paper presents the results of a study of the effect of flowsheet configurations on metallurgical results and describes a general method for developing and optimizing flowsheets used in the treatment of massive sulphide ores. The flowsheet configuration can have a significant effect on recovery and selectivity between valuable minerals and gangue minerals. Placing of intermediate products within the flowsheet, positioning of various pretreatment units, such as conditioners or regrinding mills, and the ability of the flowsheet to cope with wide swings in the feed grade and composition are the major parameters that determine the optimum flowsheet configuration. The complexity of the flowsheet is largely a function of the ore itself and of the number of final, marketable products that have to be recovered from the ore. INTRODUCTIONTechnological ExpansionThe trend of past decades has been towards larger equipment and a better understanding of the chemistry of the flotation process. Despite appreciable progress in these areas little attention was given to the study of the actual configuration of the flowsheet, although the arrangement of the flotation equipment significantly affects the overall performance of the circuit."

Jan 1, 1989

"During the development of a mining project, samples are taken for metallurgical tests. The sample can be a composite sample made of material from a selection of various drilling products or a sample from a mining test. It can be also a sample from an existing plant in order to investigate process enhancement. This sample can represent several tonnes of material which are analysed and split for use in various tests.In the current case, a composite sample of gold ore is dedicated to a Gravity Recoverable Gold (GRG) test. The properties of interest are the head grade of gold, the size distribution of the material, and the gold assay per size class. The sample is mixed and a sub-sample is taken to measure the feed properties: the size distribution and the gold assay per size class. The remaining material of the sample is subject to the first stage of concentration using the laboratory Knelson concentrator. The concentrate is analysed in its entirety, while a sample of tailings is taken for the same analysis. The remaining part of tailings is subject to grinding to feed the second and third stages of concentration. Similar sampling is performed at each stage.The concentration performances are analysed in light of these measurements. But what is the accuracy of the measurements of the properties? Pierre Gy’s theory of sampling, associated with a heterogeneity model built using the GRG test results, will answer this question. The current paper presents, through a real example, the calculation of the errors of the measurements of size distributions and gold assays performed during the GRG test. The uncertainties of the concentration performances and liberation size estimate are then calculated and their impact on the results interpretation is analysed.INTRODUCTIONDuring the development of a mining project, samples are taken for metallurgical tests. The sample can be a composite sample made of material from a selection of various drilling products or a sample from a mining test. It can be also a sample from an existing plant in order to investigate process enhancement. This sample can represent several tonnes of material which are analysed and split for use in various tests. In order to take into account the ore variability in terms of gold deportment, it is recommended to perform variability studies (Dominy, Murphy, & Gray, 2011, Dominy, 2013) using samples representing various horizons or years of production. But for a given ore type, it can be necessary to perform many tests with different operating conditions (Brochot, 2012a). In that case, the variability of the samples is not due to the heterogeneity of distribution of the deposit, but only on the heterogeneity of constitution of the primary sample. The level of confidence associated with the estimated performance parameters is directly linked to the overall error (including sampling error) of the measurements performed during the tests."

Jan 1, 2016

By Leopoldo Gutierrez, Sergio Castro, Lina M. Uribe, Janusz S. Laskowski

"The effect of sulfite and metabisulfite ions on the amyl xanthate flotation of copper-activated pyrite, in distilled water and seawater, has been studied by micro-flotation tests and redox potential measurements. The activation of pyrite was carried out varying copper ions concentration. It was found that in the presence of copper ions in solution, sulfite and metabisulfite are able to depress copper-activated pyrite at neutral or slightly acid pH. After the addition of sulfite or metabisulfite ions the resulting pH is more acidic with metabisulfite ions. A significant increase of the redox potential of the solution was observed as copper ions concentration increased. Then, the initial reducing conditions brought about by sulfite and metabisulfite ions, change abruptly to oxidizing conditions in the presence of copper ions. Under these oxidizing conditions, the metabisulfite showed to be an effective depressant for pyrite mainly in seawater. However, sulfite was a pyrite depressant in both distilled water and seawater. Based on these results, the pyrite depression by sulfoxy-depressants during the flotation of Cu/Mo ores in distilled water and seawater is discussed.INTRODUCTIONDepression of pyrite by sulfoxy-depressants (sulfite and metabisulfite) in the presence of copper ions is an important issue. This is particularly true when pyrite depression in the flotation of Cu/Mo sulfide ores is carried out in seawater. The use of lime in seawater must be avoided because the formation of magnesium hydroxy-complexes and precipitating magnesium hydroxide strongly depresses molybdenite flotation (Castro et al., 2014). In order to solve this problem, one large plant in Chile uses sodium metabisulfite (MBS) instead of lime to depress pyrite in seawater. In plant practice, this also improves molybdenite flotation since with the use of MBS the pyrite depression is carried out at pH 6-7, instead the pH 11-12 usually employed with lime.From a general point of view, pyrite exhibits some natural floatability over acidic pH ranges and may be partially floated without thiol collectors (a coating of sulfur/polysulfides has been claimed). Therefore, pyrite flotation with xanthates is usually high in the acidic pH region, but decreases greatly at alkaline pH (Leppinen, 1990; Fornasiero and Ralston, 1992; Zhang et al., 1997)."

Jan 1, 2016

By F. Cheuk, E. Krause, V. G. Papangelakis, G. A. Moldoveanu, S. Abendschein

Systematic studies have been conducted at the University of Toronto in order to evaluate lanthanide extraction from clay minerals from different geographical regions. It was found that rare earth elements (REE) are easily recovered into an aqueous solution via an ion exchange mechanism by leaching with electrolyte solutions containing monovalent cations under ambient conditions. In this study we assessed extraction levels of individual REEs as a function of initial clay composition and leaching conditions. It was found that, in spite of variations in clay origin, all clays consistently reached peak REE extraction levels with fast kinetics. However, terminal extractions were clay-specific. The feasibility of using seawater as a leaching solution and potential synergies with ammonium sulphate as a lixiviant was also investigated. Seawater was found to be inferior to using ammonium sulphate, and provided no observable synergy in leaching performance when used together. The aqueous phase trapped in leached clays was shown to contain significant amounts of REE, as demonstrated in clay washing tests. Techniques to improve the REE concentration in leachate through process variations were investigated. However, it was found that most techniques capable of increasing REE concentrations in the resultant leachate also resulted in reduced REE extraction.

Jan 1, 2014

By Mariam Melashvili, Chris Fleming, Rene Jackman

"A study was undertaken to develop a flowsheet for treating a high grade silver/gold ore body by cyanidation, CCD and Merrill Crowe precipitation, with tailings detoxification to meet stringent limits for cyanide and thiocyanate concentrations in the final discharge. In one of the flowsheets examined, free cyanide in the final leach liquor was recycled to the mill where it was hoped that it might react beneficially with fresh ore to reduce the cyanide makeup by an equivalent amount. However, laboratory results suggested that most of the cyanide recycled to the mill reacted with iron forming a soluble ferrocyanide complex. This would have had a negative impact on cost, not only because the cyanide recycled to the mill could not be claimed as a credit, but also because the presence of ferrocyanide in the final tailings meant copper sulphate had to be added to the SO2/air cyanide detoxification process to precipitate the iron cyanide. In an alternative flowsheet that was examined, recycling of cyanide to the mill was abandoned, and this allowed the milled slurry to be pre-aerated in a single mixing tank before cyanidation. During alkaline pre-aeration, any ferrous ions that are generated in the mill are oxidized to ferric ions, which, unlike ferrous ions, are inert in cyanide solution. This significantly reduced cyanide consumption and lowered costs in the detoxification of the tailings. In this paper, the cost implication of these two circuits is compared.INTRODUCTIONMost of the gold that is produced by hydrometallurgical processes is recovered by cyanide leaching. The reason for that lies in the superior thermodynamic stability of the gold cyanide complex and the favorable economics this confers on the process (Fleming, 2014). However, the gold in most of the gold-bearing ores processed is a very minor component, and therefore, the leaching response is often dominated by that of the host minerals.Many gold ores treated by the cyanidation process contain iron minerals. Cyanide reacts readily with some iron minerals forming ferrocyanide as one of the compounds. Ferrocyanide is stable when solutions are exposed to air and does not retard the dissolution of gold. In fact, it has been claimed that potassium ferrocyanide in the presence of oxygen is a weak solvent for gold (Hedley & Tabachnick, 1958). The main problem with the formation of this compound is the consumption of cyanide. Ferrocyanide contains six molecules of cyanide for each atom of iron {Fe(CN)64-} so the wasteful consumption of cyanide is greatly increased by its presence. Thiocyanate is also often produced during the reaction of certain iron sulphide minerals with cyanide, and contributes to the wasteful consumption of cyanide. In addition, environmental regulations in certain countries demand that thiocyanate be removed from the tailings, and this adds significantly to the cost of tailings treatment."

Jan 1, 2016

By Ahmad Abdollahi

Many factors affect mechanical properties of hypoeutectic Al-Si alloys. As examples the presence of impurities such as Mn and Fe due to the formation of intermetallic phases, additions of small amounts of alkaline earth metals and cooling rate in consideration of Si formation, they all have an impact on mechanical properties of hypoeutectic Al-Si alloys. In this investigation, the effect of Fe content into the specification range of A357 alloy, the addition of different modifiers consisting of Na, Sr and Ca for the alloy of A356 and different mounting techniques for separately cast test coupons of hypoeutectic Al-Si alloys using the lost wax method were studied. The results showed that using material with lower Fe content and addition of modifiers improve mechanical properties. Also different mounting techniques resulted in different mechanical properties.

Jan 1, 2004

By R. D. Brown

"AbstractOver the past five years, tax rates in the Canadian mining industry have skyrocketed upward across Canada, as both federal and provincial governments have sought to increase their share of mining revenues.However, the past few years have not only brought high tax rates to the industry, but also a number of important new federal and provincial tax incentives.In large part, these incentives ~ special credits or reduction in tax for carrying out specific exploration, processing or other activities - have helped to moderate the adverse effects of the higher tax rates and have provided inducements for exploration and processing activities which might not otherwise have been undertaken.However, the effectiveness of certain of these incentives can be questioned: our over-all tax structure now consists in large part of punitively high marginal rates with some extraordinarily generous but capricious tax reductions for specific activities and may not be in the best long-term interest of either the industry or the nation.A rational tax structure, with moderate and stable tax rates, together with reasonable incentives confined to activities specifically requiring them, could be a more effective spur to investment than the present tax and incentive jungleIntroductionIN THE YEARS since federal tax reform, the mining industry in Canada has faced a continued escalation in its tax burdens as federal and provincial governments have leapfrogged each other in imposing new and higher taxes on the industry. The result has been that marginal tax rates imposed on mining and processing activities throughout Canada have jumped to hitherto unparalleled levels."

Jan 1, 1977

By H. E. Wilde

"Zinc has been used for many years as a galvanic coating for the protection of steel. Electrochemical measurements show that zinc actually overprotects steel. The corrosion rate of DQSK (drawing quality semi-killed) steel in air saturated salt water was determined as a Junction of applied cathodic potential. The resulting data indicate that at a critical cathodic over potential of - O. 725 Vsce an acceptably low corrosion rate of less than 1 mpy occurs. Using the developed criterion, alloys of Zn/X and AL/X were produced and evaluated in galvanic contact with steel in a standard laboratory test. The results indicate that Zn /Mn, Zn /Co, AI/Mg/Si and AI/Mg/Ge alloys offer excellent galvanic protection along with (a) no hydrogen evolution, and (b) improved dissolution life over Zn coatings.IntroductionZinc coated (galvanized) steel has been successfully used in applications where bare (or painted non-galvanized) steel would suffer corrosive attack. In general, galvanic coupling to zinc, as either an anode or a coating, is an effective means for combatting steel corrosion. Because of this, the use of galvanized steel has increased markedly, stimulated primarily by automobile manufacurers seeking to extend the corrosion warranties on automobiles(1).Although effective, zinc coatings are not without a number of drawbacks which warrant efforts to improve them. For example, because of the widely differing electrode potentials between zinc and steel ( - 1.05 Vsce and - 0.60 Vscc, respectively, in air saturated NaCl solutions), the zinc corrodes at a rapid rate to protect the steel. This is reflected in the limited lifetimes of galvanized unpainted siding. The basic electrochemistry controlling the situation is shown in Figure 1, for a system controlled by oxygen reduction. The zinc corrodes sacrificially to protect the steel, while cathodically polarizing the steel to a potential near that of zinc&apos;s open circuit anode potential."

Jan 1, 1990