Showing papers in "Transactions of The Institute of Metal Finishing in 1999"
TL;DR: In this article, the authors discuss the environmental, safety and cost issues surrounding the continued use of chromates have led to increased R&D activities to find alternative materials, such as silane.
Abstract: Environmental, safety and cost issues surrounding the continued use of chromates have led to increased R&D activities to find alternative materials. Recent developments in the application of silane...
100 citations
TL;DR: The hexavalent chromium process provides unique engineering coatings in terms of wear and corrosion resistance as discussed by the authors, however, this process is under pressure due to its environmentally unfriendly attributes.
Abstract: Hexavalent chromium process provides unique engineering coatings in terms of wear and corrosion resistance. However, this process is under pressure due to its environmentally unfriendly attributes....
45 citations
TL;DR: In this paper, the study of electroless Ni-P and NiP-Si3N4 composite coatings is presented, which are obtained from a proprietary high phosphorus electroless nickel plating bath, comprising nickel sulphate, sodium hypophosphite, complexing agents and stabilizers.
Abstract: SUMMARYThe present work pertains to the study of electroless Ni-P and Ni-P-Si3N4 composite coatings. The deposits are obtained from a proprietary high phosphorus electroless nickel plating bath, comprising nickel sulphate, sodium hypophosphite, complexing agents and stabilizers. The maximum weight percent of Si3N4 incorporated in the electroless deposit is obtained at a concentration of 10 g/l in the bath. The electroless Ni-P deposits having 0%, 2.01%, 5.81% and 8.10% of Si3N4, respectively, obtained from baths containing 0, 2, 5 and 10 g/l of Si3N4, are characterized by optical microscopy, XRD and TEM. Hardness is found to increase with the incorporation of Si3N4 at all heat treatment temperatures studied. Also hardness increases with an increase in weight percent of Si3N4 incorporated in the deposit. The analyses of the composite coatings by XRD and TEM reveal that the inclusion of Si3N4 particles does not change the amorphous nature of the Ni-P matrix.
27 citations
TL;DR: In this article, a useful coating technology for electroless Ni-1.5wt%P has been developed, which can work normally for more than 5 turnovers with a plating rate of 20 μm/h.
Abstract: SUMMARYA useful coating technology for electroless Ni-1.5wt%P has been developed. The bath can work normally for more than 5 turnovers with a plating rate of 20 μm/h. In the as-deposited condition, Ni-1.5wt%P deposit is a supersaturated solid solution of P dissolved in a nanocrystalline Ni matrix with a grain size of several nanometers. The microstructure transformed into a larger grain size Ni matrix with dispersive Ni3P precipitates with increasing the heat treatment temperature. Ni-1.5wt%P deposit possesses as-deposited hardness and wear resistance superior to Ni-10.5wt%P deposit. The microhardness and wear resistance can be further improved by proper heat treatment. The optimum wear resistance of Ni-1.5wt%P deposit corresponds to its peak hardness (annealing at 375°C for 1 h), whereas for Ni-10.5wt%P deposit the optimum wear resistance is obtained after annealing at 650°C for 1 h. Ni-1.5wt%Ppossesses a corrosion resistance in NaOH solution superior to conventional medium and high phosphorus deposits, ...
22 citations
TL;DR: In this article, the corrosion properties of Ni-Sn-P amorphous deposits were investigated in 0.5 M H2SO4, 5% HCl, 10% NaCl and 50% NaOH.
Abstract: Ternary amorphous Ni-Sn-P alloys were prepared by electroless plating. The influences of technological conditions on the deposition rate and concentration of deposits were studied in detail. The structure of deposits were examined by X-ray diffraction. The addition of tin into Ni-P alloys improved the formability of the amorphous phase. The corrosion properties of deposits immersed in 0.5 M H2SO4, 5% HCl, 10% NaCl and 50% NaOH were determined. It has been found that the addition of Sn into Ni-P deposits did not usually improve the corrosion resistance compared with that of electroless amorphous Ni-P deposits. However, the corrosion resistance of Ni-Sn-P amorphous deposits was as good as that of stainless steel, at last.
17 citations
TL;DR: A number of possible non-chromate conversion coating formulations have been studied to examine their efficacy as replacements for chromate-based coating treatments on electrodeposited zinc-nickel alloys.
Abstract: A number of possible non-chromate conversion coating formulations have been studied to examine their efficacy as replacements for chromate-based coating treatments on electrodeposited zinc-nickel alloys. Data have been collected from both electrochemical and conventional salt fog corrosion tests. In the latter tests all the alternative non-chromate systems studied delayed the onset of the corrosion of the zinc-nickel coating itself but only the simple molybdate and the permanganate/molybdate dual treatment brought about improvements in times to red rusting of the steel substrate. The electrochemical evaluations suggested that simple molybdate-treated surfaces act as only moderate barriers to the chloride environments. Of the two dual treatments, permanganate/molybdate behaved similarly to the simple molybdate treated surfaces in the electrochemical tests, but the molybdate/permanganate was more protective, although this was not exhibited in the salt fog corrosion tests.
16 citations
Abstract: The technique of Coulometry is based on the fundamental concepts incorporated in Faraday's Laws and is therefore a referee method for coating thickness determinations. The design of coulometric dis...
15 citations
TL;DR: In this article, the electrodeposition of Ni-W alloy has been studied on the glassy carbon electrode by the cyclic voltammetry and potentiostatic step methods.
Abstract: SUMMARYThe electrodeposition of Ni-W alloy has been studied on the glassy carbon electrode by the cyclic voltammetry and potentiostatic step methods. It has been found that electrodeposition of Ni-W alloy involves an intermediate valence tungsten oxide which inhibits hydrogen evolution. Ni-W alloy electrodeposition occurs by a mechanism involving progressive nucleation followed by three dimensional growth.The structures of nickel-tungsten alloy deposits were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD results from Ni-W alloy deposits reveal a face-centered cubic solid solution, the microstructure of the deposits exhibit (111) preferred orientation. The lattice constant and microhardness of Ni-W alloy deposit increase as the tungsten content increases, the XPS results of Ni-W alloy deposits indicate that the nickel and tungsten of the deposits exist in the metallic state, but the Ni-W alloy deposit with a tungsten content of 40.7% is an intermetallic compound. Th...
15 citations
TL;DR: In this article, the zinc-cobalt coatings have been used as a replacement for brass in the cord-making operation of radially reinforced steel cord. But the results showed that brass coatings were superior in preventing red rust formation on the steel.
Abstract: SUBJECTTyres which are radially reinforced with high tensile steel cords need to develop a bond between the rubber and the steel. Brass coatings on the cord are currently used to promote the bond but deterioration takes place with time and corrosion of the underlying steel occurs eventually. Zinc-cobalt coatings have been used as a replacement for brass. These coatings are capable of being drawn in the cord making operation provided that the cobalt content is 1.5wt%. Pull-out tests after vulcanising show that zinc-cobalt promotes similar adhesive strengths to that achieved with brass coatings. After ageing in warm moist conditions for up to 16 days the zinc-cobalt coating maintained higher levels of adhesion than brass. In tyre tests the zinc-cobalt coatings were superior in preventing red rust formation on the steel
14 citations
TL;DR: In this article, a rotary electrode was used for Ni-B alloy plating by electrodeposition, and the amount of codedeposited B can he calculated from v0.7 and l/I, regardless of the electrode potential.
Abstract: SUMMARYWe electrodeposited Ni-B ahoy films using a rotary electrode under various plating conditions and investigated the mechanism of the codeposition of B into the plated films by analyzing the relationship between the electrodeposition conditions and the composition of the plated films, as well as by analyzing electrochemical measurements. We reached the following conclusions: 1) In Ni-B alloy plating by electrodeposition, use of a rotary electrode expands the useful current density regions compared to a static bath.2) Unionized TMAB is present in the plating solution, and the deposition rate of B is related to the thickness of the diffusion layer at the cathode surface, regardless of the electrode potential. Accordingly, the amount of codedeposited B can he calculated from v0.7 and l/I, i.e., peripheral speed and current density.
14 citations
TL;DR: The effects of 2-butyne-1, 4-diol and three compounds of different valence sulfur (sodium benzenesulfonate, sodium benzenedesulfinate, and thiosalicylic acid) on the surface morphology and crystal morphology were studied in this paper.
Abstract: The effects of 2-butyne-1, 4-diol and three compounds of different valence sulfur (sodium benzenesulfonate, sodium benzenesulfinate and thiosalicylic acid) on the surface morphology and crystal ori...
TL;DR: In this article, the authors describe room temperature molten salts which can be used for aluminium electrodeposition and show that they have a number of advantages over those described in the literature including lower water sensitivity, greater ease of purification and greatly reduced cost.
Abstract: SUMMARYThis work describes novel room temperature molten salts which can be used for aluminium electrodeposition. We have characterised the conductivity as a function of the bath composition and shown that the changes in conductivity occur because of an equilibrium between [Al2Cl7] and [AlCl2 The voltammetry of the optimum melt is analysed together with the mechanism of nucleation. Hull cell tests were performed and the morphology of the deposits was analysed using scanning electron microscopy. These room temperature molten salts have a number of advantages over those described in the literature including lower water sensitivity, greater ease of purification and greatly reduced cost. The electrodeposition of adherent, dull aluminium is demonstrated. It is also shown that soluble aluminium anodes can be used. These novel baths form a viable alternative to conventional methods of depositing aluminium.
TL;DR: In this article, preliminary experiments were carried out in order to electrodeposit good quality and satisfactory nickel plate on to copper substrates from gluconate baths, and the effects were investigated of bath co...
Abstract: Preliminary experiments were carried out in order to electrodeposit good quality and satisfactory nickel plate on to copper substrates from gluconate baths. The effects were investigated of bath co...
TL;DR: In this article, the growth of anodic films on aluminium in disodium tetraborate, so-called alkaline anodizing, has been examined by transmission electron microscopy of plan views of stripped anodic film and ultramicrotomed sections of the anode film attached to the aluminium substrate.
Abstract: SUMMARYThe growth of anodic films on aluminium in disodium tetraborate, so-called alkaline anodizing, has been examined by transmission electron microscopy of plan views of stripped anodic films and ultramicrotomed sections of the anodic film attached to the aluminium substrate. For the conditions selected, initial film growth proceeds at relatively high efficiency under galvanostatic anodizing conditions; during the following constant voltage period, porous anodic film results. The latter arises through penetration of electrolyte species into the alumina film, with eventual focus of the field in such regions, establishing conditions for field assisted dissolution, probably thermally enhanced, and development of a porous anodic film. The cell walls adjacent to the pores have a feathered appearance, which results from mechanical disruption of the film material at the pore base under the high field.
TL;DR: The effects of saccharin and three kinds of pyridine derivatives [pyridine, 3-amino-pyrididine and pyridinium-1-propane-3′-sulfonate (PPS)] on the surface morphology and crystal orientation of nickel are discussed in this paper.
Abstract: The effects of saccharin and three kinds of pyridine derivatives [pyridine, 3-amino-pyridine and pyridinium-1-propane-3′-sulfonate (PPS)] on the surface morphology and crystal orientation of nickel...
TL;DR: In this paper, the properties and morphol. of Zn-Co alloys contg 0.8-1.1% were investigated and the percentage Co in the alloy decreased with increasing c.d.
Abstract: The compn., properties and morphol. of Zn-Co alloys contg. 0.8-1.1% Co deposited from an alk. sulfate bath contg. triethanolamine and gelatin have been investigated. A bath contg. a higher Co content produced an alloy with a higher Co content. The percentage Co in the alloy decreased with increasing c.d. A higher Co content in the alloy increased the alloy hardness. Morphol. of the alloy deposits depended on the amt. of Co in the alloy.
TL;DR: In this article, a thick passive film showing interference colours has been obtained on 304 stainless steel in sulfuric acid solution without Cr 6+ ions by applying alternating square wave polarization (XPS).
Abstract: A thick passive film showing interference colours has been obtained on 304 stainless steel in sulfuric acid solution without Cr 6+ ions by applying alternating square wave polarization. An investigation of the chemical composition and the distribution of valence states in the profile of the film has been carried out by using XPS. A mechanism for the colouring process is proposed.
TL;DR: In this article, the effects of plating variable, such as particle concentration in the bath, cathode current density, stir rate and stir type on particle content in the composite coatings (Vp) were investigated.
Abstract: Cu-MoSi 2 composite coatings were obtained by an electrodeposition technique from a conventional acid copper sulfate bath. The effects of plating variable, such as particle concentration in the bath, cathode current density, stir rate and stir type on particle content in the composite coatings (Vp) were between Vp and stir rate, particle concentration in the bath and current density were related to the nature of incorporated particles (the density and electrical resistivity). Moreover, stir type showed a great effect on Vp of Cu-MoSi 2 . The codeposition rate and internal stress of Cu-MoSi 2 composite coatings were greatly influenced by plating variables. The physicomechanical properties electrical resistivity, hardness and wear resistance of Cu-MoSi 2 and Cu-Al 2 O 3 were determined. It was established that microhardness and wear resistance increased with the increase of Vp for both Cu-MoSi 2 and Cu-Al 2 O 3 . The hardness and electrical resistivity of Cu-MoSi 2 were lower compared with Cu-Al 2 O 3 . However, it was more abrasive than Cu-Al 2 O 3 .
TL;DR: In this article, the anomalous type of codeposition in which the less noble metal, Zn, deposits preferentially to the more noble one was investigated, and a comparison between the experimental and theoretical (calculated) polarization curves during codepposition was utilized to provide an explanation of the phenomenon.
Abstract: Preliminary experiments were carried out in order to electrodeposit a sound and satisfactory Zn-Co alloy from citrate baths. Highly adherent Zn-Co plates, fine-grained, white-grey and with metallic lustre and were deposited on to a steel substrate from an acidic citrate (Zn-Co)-1 bath which contains: CoSO 4 .7H 2 O 0.26 mol.l -1 , citric acid 0.1 mol.l -1 and tri sodium citrate 0.19 mol.l -1 at pH = 5.0. The Zn-Co alloys codeposited from the citrate bath belong to the anomalous type of codeposition in which the less noble metal, Zn, deposits preferentially to the more noble one. A comparison between the experimental and theoretical (calculated) polarization curves during codeposition was utilized to provide an explanation of the anomalous phenomenon. Under the chosen condition of current density (2.0 A dm -2 ), duration (20 min.) and temperature (25°C), pH = 5, the current efficiency of the alloy plating (F Zn-Co = 62%) was much lower than those observed for either of the parent metals (F Co = 89% and F Zn = 97%). The Co% in the alloy increases with increase of either its content in the bath or of the bath temperature. On the other hand, Co% in the alloy increases with decreasing current density or decreasing pH. X-ray diffraction analysis showed the presence of two phases for the alloy codeposited from (Zn-Co)1 bath (hexagonal and monoclinic). Superimposing a.c. on d.c. during Zn-Co codeposition greatly improves the uniformity and the levelling of the deposit.
TL;DR: In this paper, the fundamental principles underlying the removal of organic contamination from metal surfaces with organic solvents are discussed and a simple mechanism postulated to explain the gradual decrease in the decontamination rate that occurs as the cleaning process progresses.
Abstract: SUMMARYExperimental results are presented which allow comparison between the cleaning performance of recently available environmentally friendly solvents and traditionally used solvents. Particular emphasis is given to considering the removal of different kinds of grease contamination from components with blind holes or crevices. The fundamental principles underlying the process of removal of organic contamination from metal surfaces with organic solvents are discussed and a simple mechanism postulated to explain the gradual decrease in the decontamination rate that occurs as the cleaning process progresses. It is considered most likely that the primary role of ultrasonification in the cleaning of metals is to promote detachment of contaminant from the surface rather than enhanced transport of dissolved material away from the surface/solvent interface.
TL;DR: In this paper, a Monte Carlo simulation using a diffusion-based exposure assessment model was employed to aid forecasting of solvent vapour concentrations in the workspace during wipe cleaning of metal component, and the results obtained using Monte Carlo forecasts are considered most useful when taken in conjunction with the relevant occupational exposure limits for the solvents in question.
Abstract: A Monte Carlo simulation using a diffusion based exposure assessment model was employed to aid forecasting of solvent vapour concentrations in the workspace during wipe cleaning of metal component. Range values for the important variables were chosen so as to be appropriate for wipe cleaning with either highly volatile solvents such as Vertrel-MCA or HFE71DE or with less volatile solvents such as n-propylbromide (nPBr). Emphasis is put on confirming that the range values of variables and the distributions taken are applicable to the workplace environment so that the simulation values obtained are reasonable estimates of the true vapour concentrations. The results obtained using Monte Carlo forecasts are considered most useful when taken in conjunction with the relevant occupational exposure limits for the solvents in question
TL;DR: In this article, the preparation of conductive particles (5 ∼ 7 μm diameter ) by electroless nickel plating has been investigated and uniform coverage of deposited nickel on the particles was obtained by using ammonium acetate as a complexing agent, and surface coverage was further improved without coagulation of particles by treatment with a surface active agent before their introduction to the plating bath.
Abstract: SUMMA RY - Mechanical solderless chip packaging with small gold bumps 1 has increased in electronic devices. The preparation of conductive particles (5 ∼ 7 μm diameter ) by electroless nickel plating has now been investigated. Generally, batch type electroless plating is applied to provide conductivity on nonconductors. Since the surface areas of particle s are much larger than the bulk substrate, accordingly the electroless plating bath becomes unstable. The continuous dropping method has therefore been applied, in the preparation of conductive particles Uniform coverage of deposited nickel on the particles was obtained by using ammonium acetate as a complexing agent, and surface coverage was further improved without coagulation of particles by treatment with a surface active agent before their introduction to the plating bath.
Abstract: Ni-Mn-Fe alloys were electrodeposited from three compositionally altered Ni-Mn electrolytes containing a small amount of FeSO 4 (NH 4 ) 2 SO 4 .6H 2 O (10gl -1 ). Texture development in the resultant co-deposits was investigated with opticical colour polarisation microscopy. Addition of Fe in the electrodeposited Ni-Mn system results in the development of additional textures. Most of the samples show three different types of textures though the texture types are characteristic of the bath composition and deposition CD.
TL;DR: The significance and importance of solution conductivity for electrodeposition solutions and their efficient use are discussed in this article, where the dearth of reliable data is revealed and a collation of available data is provided for the commoner metals and solutions.
Abstract: The significance and importance of solution conductivity for electrodeposition solutions and their efficient use are discussed. The dearth of reliable data is revealed and a collation of available data is provided for the commoner metals and solutions.
TL;DR: In this article, the authors compare the evaporation rates of the traditional solvents under varying conditions to those of the proposed replacement substances and give a detailed discussion given of the usefulness of the Evaporation models to predict emission rates.
Abstract: SUMMARYIn replacing traditionally used solvents for external wipe cleaning applications with newer and more environmentally friendly solvent systems, account has to be taken of their volatility since this has a great bearing on the cost of the cleaning process as well as on occupational health hazards to operatives. To determine the concentrations of solvent vapour which will be produced in the workspace and to make sure that these do not exceed occupational exposure limits, it is necessary to know not only the workspace ventilation conditions but also the source evaporation rate of the solvent used. A study carried out to compare the evaporation rates of the traditional solvents under varying conditions to those of the proposed replacement substances is reported and a detailed discussion given of the usefulness of evaporation models to predict emission rates.
TL;DR: The speed of metal deposition and dissolution has been studied extensively in the literature, see as discussed by the authors for a detailed review of the main sources and methods of metal deposition and dissolution.
Abstract: (1999). The Speed of Metal Deposition and Dissolution. Transactions of the IMF: Vol. 77, No. 5, pp. 209-211.
TL;DR: In this article, a thin films of Ni-Fe alloys of various compositions have been deposited potentiostatically from an alkaline sulfate bath solution containing the sodium salt of ethylene diamine tetraacetic acid (EDTA) and triammonium citrate (TAC).
Abstract: SUMMARYThin films of Ni-Fe alloys of various compositions have been deposited potentiostatically from an alkaline sulfate bath solution containing the sodium salt of ethylene diamine tetraacetic acid (EDTA) and triammonium citrate (TAC). The complex nature of the bath solution was analyzed by cyclic potentiometric and spectrophotometric studies. The composition of the alloy was found to vary with the plating bath composition (Ni/Fe), plating potential and the concentration of complexing agent (EDTA). XRD studies showed that alloys are solid solutions of Fe in Ni (γ-Phase) with fcc structure, free from oxides/hydroxides and pore free. The surface analysis by SEM revealed the nucleation by crystallites giving smooth deposit. The magnetic properties (Hc, Ms and squareness ratio) were evaluated from the parallel (in-plane) and perpendicular hysteresis loops. Plating conditions were optimized to plate good quality thin films of Ni-Fe alloy with 80% Ni(Permalloy) with tailor made magnetic properties which suit ...
TL;DR: In this article, the interaction of the Cu 2 O adsorbed with Na 2 S n (n = 1-4 ) during the formation of Cu 2-x S coatings has been investigated by cyclic voltammetry.
Abstract: The interaction of the Cu 2 O adsorbed with Na 2 S n (n = 1-4 ), during formation of the Cu 2-x S coatings has been investigated by cyclic voltammetry. The summarized reaction of this process has been shown to correspond to the equation: Na 2 S + Cu 2 O ad + H 2 O → Cu 2 S ad + (n-1)S 0 + 2NaOH, where S 0 /Cu=(n 1)/2. Such a stoichiometry of reaction ca be explained by the formation of an intermediate the adsorbed polysulphide of Cu(1) and by its subsequent decomposition into Cu 2 S and S 0 . When a thicker coating is being formed, i.e., when the surface being coated is repeatedly immersed into an ammoniate solution of Cu (1) and S 0 fully bounded: S 0 ad + 2Cu + → CuS + Cu 2 + . At the same time due to different solubility products (L=2.5-10 and 6.3-10 for Cu 2 S and CuS respectively), an exchange CuS ad + 2 (1-x)Cy + →Cu 2-x S ad +(1-x)Cu 2+ occurs. After formation of Cu 2+ . parallel processes characteristic for the interaction of Cu(II) with Na 2 S n start to take place, during which S is also formed.
TL;DR: In this article, three kinds of complexing agents were selected to investigate their effects on the morphology and porosity of electroless nickel (EN) deposits on a mild steel substrate.
Abstract: Three kinds of complexing agents were selected to investigate their effects on the morphology and porosity of electroless nickel (EN) deposits on a mild steel substrate. The porosity of the EN coating was tested as a function of the variety of complexing agents with both an electrochemical technique and commonly used chemical spot tests. Meanwhile, the morphology and surface roughness of deposits were examined by atom force microscopy (AFM). It was found that the more stable is the nickel complex, the lower the roughness and the less the porosity of the coating. The reason for this is discussed, considering the complexing agent's effect on the deposition process of EN.
TL;DR: In this paper, the interaction of Cu 2 O + Cu(OH) 2 adsorbed with Na 2 S 4 was investigated using the methods of cyclic voltammetry and radiochemistry (35 S).
Abstract: The interaction of Cu 2 O + Cu(OH) 2 adsorbed with Na 2 S 4 in the course of formation of Cu 2 x S coatings by a cyclic method has been investigated using the methods of cyclic voltammetry and radiochemistry ( 35 S). (One cycle of Cu 2 x S coating formation consists of the treatment of the surface to be coated in a solution of Cu (I) + Cu (II) ammoniates, rinsing-hydrolysis and sulphidation in Na 2 S 4 solution). Only 25% of the Cu 2 x S coating has been found to be formed due to adsorption of Cu (I) + Cu (II) and up to 10% due to S 4 2 adsorption. The remaining portion (∼ 65%) of the coating is formed due to interaction of Cu (I) with elemental sulphur S 0 ad +2Cu + → CuS ad +Cu 2+ and the exchange occurring in the course of repeating the cycle CuS ad +2(1-x)Cu + → Cu 2-x S ad +(1-x) Cu 2+ . Elemental sulphur is supposed to be formed in a sulphidation stage through individual and mixed intermediates of Cu (I) and Cu (II) polysulphides as well as during the hydrolysis of the adsorbed S 4 2 (≤10% S o ).