Search results

Corrosion data of the widely used silver brazing alloys (BAg‐1 and BAg‐3) of the American Welding Society’s (AWS) specification are scant in literature. Deals with the study of the corrosion behaviour of these alloys in different environments with particular emphasis on the industrial and marine atmospheres.

The corrosion of boiler drums is intimately linked to the deterioration of the protective oxide film separating the steel substrate from the boiler fluid, which often contains constituents conducive to corrosion. Various forms of corrosion occur in the boiler drums and such occurrences can be due to:

Introduction It is well established that Si in silicon bronzes imparts high strength and corrosion resistance which are essential requirements for applications in hydraulic pressure lines, heat exchangers, propeller shafts, storage tanks and other equipments for chemical industries. They have high corrosion resistance towards marine environments, but possess inferior corrosion resistance in sulphide bearing atmosphere although more resistant to stress corrosion cracking and season cracking than brass on exposure to polluted atmospheres. In general, corrosion resistance of alloys depends on alloy chemistry, heat treatment schedule, presence of second phase, precipitation morphology and specific environment. However, studies on influence of heat treatment and variation of silicon content in (Binary) Cu‐Si alloys with particular reference to their corrosion resistance in chloride and sulphide bearing environments are scanty in literature. The present work has been designed to study the corrosion behaviour and to generate data on three types of commercially important Cu‐Si alloys in 3.5 per cent sodium chloride and 1 per cent sodium sulphide solutions.

Silicon plays a vital role in the corrosion resistance of Cu‐Si alloys by forming a copper silicide protective layer on the surface of the alloys in natural seawater but, for the higher percentage of silicon content in the alloy (10 wt. per cent), sometimes, with the synergistic effect of the silicide layer along with free silicon, protection takes place. Electrochemical behaviour test using computerized potentiostat/galvanostat (PARC Model No. 273, EG&G, USA) immersion test in natural seawater and X‐ray diffraction analysis using Simons D‐500 diffractometer support the phenomenon.

Iron and silicon are the two inherent impurities present in commercial aluminium which impair its corrosion resistance. Influence of silicon/iron ratio present in aluminium alloys containing different amounts of silicon has been studied through electrochemical polarization in some inorganic and organic acids (0.1 N). It has been observed that Si/Fe ratio has potential role on corrosion rates in different acids studied.

Stainless steels are very unique in that they offer a wide range and combination of resistance to corrosion, resistance to oxidation at high temperature and good mechanical properties at room temperature. With rapid industrialization all over the world, these very properties have led to extensive use of stainless steels in different industries. Austenitic stainless steels containing molybdenum exhibit corrosion resistance in both sulphuric acid and nitric acid. Stainless steel undergoes severe attack in sulphuric acid having concentrations in the range of 20‐85 per cent, whereas they are immune to nitric acid in any concentration. However, sensitized stainless steels are prone to intergranular attack in acids, even in nitric acid. Further, the attack is aggravated in the presence of aggressive ions. Study of the behaviour of stainless steels in a mixture of acids (nitric and sulphuric acid) is lacking in the literature. This paper, therefore, discusses the performance of AISI‐316 and 316‐L in sulphuric acid and nitric acid and a mixture thereof at room temperature. It is observed that the steels are quite resistant to sulphuric acid and nitric acid, but in the acid mixture they are not so resistant, especially in AISI‐316 SS in respect of corrosion resistance, even in acid mixture containing C1^‐ and Cu⁺⁺ ions.

High strength low alloy steels have attained wide acceptance as structural materials. Research and development have led to different corrosion preventive methods. High strength low alloy (HSLA) of composition C(0.4%), Mn(0.7%), Si(0.25%). Cr(0.8%), Ni(1.7%) was selected for this study. Epoxy iron oxide, epoxy micaceous iron oxide (MIO), zinc‐rich epoxy and zinc ethyl silicate were used for painting the HSLA panels (150mm × 100mm × 3mm). Physical properties such as film thickness, specific gravity, viscosity, drying times of paints were evaluated and salt spray test, AC impedance and metallographic examination were carried out. Performance of zinc ethyl silicate coating over HSLA was found to be the best followed by epoxy micaceous iron oxide system.

The purpose of this paper is to focus on diversification between electrical parameters determined on the basis of instantaneous impedance measurements within the activation and reactivation scan of dissolution of sensitized AISI 304 stainless steel during a proceeding intergranular corrosion process.

The investigations were carried out by means of dynamic electrochemical impedance spectroscopy (DEIS). DEIS measurements were conducted “on‐line” while the samples were polarized in agreement with a measurement procedure presented in the ASTM G108‐94 standard, in order to guarantee conditions equivalent with the DL‐EPR tests performed on AISI 304 stainless steel.

Performed researches revealed the advantages of the DEIS technique over standard double‐loop electrochemical potentiokinetic reactivation (DL‐EPR) tests in the field of intergranular corrosion investigations. Application of the DEIS technique made it possible to trace instantaneous changes in the examined system's impedance versus potential during the intergranular corrosion process. The form of recorded DEIS spectra and obtained distribution of measurement frequencies within the reactivation potential range were equivalent to those obtained for pure iron dissolution in sulfuric acid medium. As a result, instantaneous changes of electrical double layer capacitance and charge transfer resistance as a function of potential have been obtained in the range of activation and reactivation scans.

The paper provides information regarding diversification between the electrical double layer capacitance and the charge transfer resistance determined for sensitized AISI 304 stainless steel with respect to polarization conditions during the standard DL‐EPR test, which were obtained in order to evaluate the susceptibility to intergranular corrosion.

This paper aims to investigate the parametric study of addition of snail shell particles (SSp) and bath temperature on the properties of Zn-ZnO-SSp composites coating.

Bath temperatures of 60°C and 90°C and SSp of 0, 5, 10, 15, 20 and 25g were used in the electrodeposition. The microstructure, electrochemical, wear and hardness values of the coated samples were determined.

Highest coating thickness of 240 µm, 277 per cent improvement in hardness values, 66.67 per cent improvement of wear rate were obtained at bath temperature of 60oC and 15gSSp addition over that of the uncoated sample. There was improvement in corrosion resistance after composites coating. Maximum improvement in the properties was obtained at bath temperature of 60°C at 15gSSp addition.

It has been established in this work that bath treatment and SSps improved the properties of the developed coating.

This study aims to analyze the factors that determine non-farm enterprise diversification among farm households in Ethiopia. It extends the analysis by examining enterprises and using pooled data, which has the capacity to generate more accurate outcomes. The existing empirical evidence has focused on all non-farm activities, based on single period, single region data. Much of the existing empirical evidence is based on small-scale and location-specific sample surveys that do not demonstrate the characteristics of aggregate populations.

The empirical analysis was conducted using a quantitative method. To cater to the censoring nature of participating in non-farm enterprise activities, a panel data double-hurdle model is used to a representative sample of 3,594 Ethiopian rural households.

The study finds that the age of household head, household size, distance to the market, social capital and access to credit, are determinants for owning one or more non-farm enterprises. The level of income from these enterprises is then determined by the age and education level of the household head, household size, agricultural equipment, distance to markets and access to credit.

This study brings to light factors that influence households to participate in non-farm enterprises and the determining factors for the income level.

Non-farm activities are an important source of household income and a driver of development. This paper provides empirical evidence on factors that determine enterprise ownership using panel data.