Corrosion characteristics of cobalt-silicon nitride electro composites in various corrosive environments
TL;DR: In this paper, the corrosion characteristics of electro codeposited cobalt-silicon nitride composites in neutral sodium chloride and sulphuric acid solutions are presented, and the electro composites showed greatly improved corrosion resistance over pure cobalt in nondeaerated 3.5% sodium chloride solution, but they induced significantly less galvanic corrosion on steel in the same medium.
Abstract: The corrosion characteristics of electro codeposited cobalt-silicon nitride composites in neutral sodium chloride and sulphuric acid solutions are presented. The electro composites showed greatly improved corrosion resistance over pure cobalt in nondeaerated 3.5% sodium chloride solution, but they induced significantly less galvanic corrosion on steel in the same medium. Galvanic current and dissolution current measurements showed a linear variation with the cathode-to-anode area ratio, while the galvanic potential showed a logarithmic variation with the same. Composites of cobalt-silicon nitride also showed improved passivation properties in 1 N sulphuric acid.
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TL;DR: In this article, a flat absorber black nickel alloy coating was developed on stainless steel by electrodeposition from a bath containing nickel, zinc and ammonium sulphates; thiocyanate and sodium hypophosphite for space applications.
Abstract: A new process of flat absorber black nickel alloy coating was developed on stainless steel by electrodeposition from a bath containing nickel, zinc and ammonium sulphates; thiocyanate and sodium hypophosphite for space applications. Coating process was optimized by investigating the effects of plating parameters, viz concentration of bath constituents, current density, temperature, pH and plating time on the optical properties of the black deposits. Energy dispersive X-ray spectroscopy showed the inclusion of about 6% phosphorous in the coating. The scanning electron microscopy studies revealed the amorphous nature of the coating. The corrosion resistance of the coatings was evaluated by the electrochemical impedance spectroscopy (EIS) and linear polarization (LP) techniques. The results revealed that, phosphorous addition confers better corrosion resistance in comparison to conventional black nickel coatings. The black nickel coating obtained from hypophosphite bath provides high solar absorptance (αs) and infrared emittance (ɛIR) of the order of 0.93. Environmental stability to space applications was established by the humidity and thermal cycling tests.
6 citations
TL;DR: In this paper, the effect of cetyltrimethylammonium bromide (CTAB) as a cationic surfactant on the cathodic process was investigated.
Abstract: Electrodeposition of SiC particles in a cobalt matrix in the presence of cetyltrimethylammonium bromide (CTAB) as a cationic surfactant has been carried out. The inhibiting effect of CTAB (0–1·1 mM) on the cathodic process was observed during the establishment of polarisation curves in galvanostatic and potentiodynamic measurements. The surfactant enhanced SiC incorporation into the matrix from ∼5 vol.‐% in the absence of CTAB to ∼30 vol.‐% at 1·1 mM CTAB for two current densities (0·5 and 1·0 A dm−2). The presence of cationic surfactant in the bath decreased the adsorption of Co2+ ions on SiC, but increased Br− adsorption was simultaneously observed. Current efficiencies were correlated with Co2+/Br− molar ratios for the ions adsorbed on the particles. The structure of the composite coatings was studied microscopically. Microhardness of the deposits (200–500 HV) was also determined.
5 citations
TL;DR: In this paper, a simple and easy method to prepare well-dispersed cobalt-plasma polymerized hexamethyldisilazane (Co-pp HMDSN) nanocomposites is presented.
Abstract: A simple and easy method to prepare well-dispersed cobalt–plasma polymerized hexamethyldisilazane (Co–pp HMDSN) nanocomposites is presented. A hybrid physical vapor deposition (PVD) and plasma enhanced chemical vapor deposition (PECVD) technique was used to prepare finely dispersed Co–pp HMDSN nanocomposites. The metal filling factor could be varied from 4% to 34%. Structural investigations were performed using transmission electron microscopy (TEM) and X-ray diffractometry (XRD). They revealed the presence of amorphous cobalt nanoparticles of size ~ 2–3 nm at lower filling factor, whereas crystalline CoO nanoparticles of size ~ 6 nm were observed at higher filling factor. Energy dispersive X-ray spectroscopy (EDX) and profilometry were employed to determine the filling factor. Compositional analysis using Fourier transform infrared (FTIR) spectroscopy indicated the presence of Si O and Si C bonds in the polymer matrix. The influence of oxygen was observed in all nanocomposites. With the increase in filling factor the polymer matrix was significantly modified. A set of well-dispersed Co–pp HMDSN nanocomposites with varying metal filling factors was prepared which is suitable as precursor for calcination. As the functional properties of the calcinated nanocomposites are dependent on the properties of the precursors, the importance of a detailed study of the precursors for calcination is emphasized. A simple and generalized procedure to introduce well-dispersed metal nanoparticles into a polymer matrix is demonstrated.
4 citations
01 Apr 2021
TL;DR: A brief review on nanocomposite coating in industry with focus on the effect, role, types and its application is provided in this article, where the authors provide a brief review of nanocomposition coating.
Abstract: Study on the nanocomposite coating is on increase due to their multifunctional
characteristics in industries. Nanocomposite coatings are made up of two or
more immiscible nanomaterials which can also be detached with the purpose
of providing mechanical properties that make them strong. It has also been of
great importance in minimizing deterioration and biofouling impact. This
coating has a great aplication in automotive, aerospace, seawater condensers
and tubes, electronic industries, water electrolysis, energy generation.
Furthermore, it has also enhanced the growth of paints and its properties in
industrial production. Due to its properties, they are utilized in contruction
firm, medical area, etc. Despite the aforementioned, nanocomposite coatings
has increase in recent years as a result of advancements of nanoparticle
manufacturing processes.This paper provides a brief review on nanocomposite
coating in industry with focus on the effect, role, types and its application.
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TL;DR: In this paper, the effect of graphite and silicon carbide reinforcements on the pitting behavior of a graphite/aluminum (Gr/Al) and SiC/Al matrix composites was examined.
Abstract: This paper examines the effect of graphite and silicon carbide reinforcements on the pitting behavior of graphite/aluminum (Gr/Al) and silicon carbide/aluminum (SiC/Al) metal matrix composites. Electrochemical corrosion tests were performed on both Gr/Al and SiC/Al composite specimens. Identical tests were completed on powder metallurgy processed aluminum and wrought aluminum of the same composition. The electrochemical behavio of the SiC/Al composites was essentially identical to that of the powder processed and wrought aluminum alloys; however, the pitting attack on the SiC/Al composites was distributed more uniformly across the surface, and the pits penetrated to significantly less depths. The presence of graphite in the Gr/Al composites did not cause an electropositive shift in corrosion potential as anticipated, but caused a substantial decrease in resistance to passive film breakdown. This effect is the predominant reason for the poor performance of Gr/Al composites in marine environments.
139 citations
TL;DR: In this paper, the effect of phase on the corrosion behavior of metal matrix composites has been studied in, both in the presence and absence of dissolved oxygen, and the results show that pitting susceptibility is about the same for the composites and their corresponding alloys, except for Al 2024.
Abstract: The effect of the phase on the corrosion behavior of metal matrix composites has been studied in , both in the presence and absence of dissolved oxygen. Anodic polarization behavior has been determined, and pitting potentials have been measured for three composite systems: 2024, 6061, and 5456. General corrosion behavior and the effects of anodizing on the corrosion resistance of the composites have been studied by a‐c impedance techniques. The results show that pitting susceptibility is about the same for the composites and their corresponding alloys, except for Al 2024. In this system, the composite is less resistant to pit initiation than the corresponding wrought aluminum alloy. General corrosion is more significantly affected by the presence of oxygen than by the phase. In the absence of oxygen, corrosion resistance is improved for both the alloys and composites. In addition, the corrosion resistance of the composites can be improved by anodizing.
125 citations
TL;DR: Pit morphology of Al 5456, Al 6061, SiCw/Al 5456 (UNS A95456), Al 60 61 (UNs A96061) and SiCws/Al 6061 is studied in this article, in order to compare pitting processes of Si cw/al matrix composites with that of corresponding unreinforced alloys.
Abstract: Pit morphology of Al 5456 (UNS A95456), Al 6061 (UNS A96061), SiCw/Al 5456, and SiCw/Al 6061 is studied in order to compare pitting processes of SiCw/Al metal matrix composites with that of corresponding unreinforced alloys. Work on anodized samples of Al 6061 and SiCw/Al 6061 is also included. Pits on the composites are significantly more numerous, shallow, and widespread than on the monolithic materials. Studies of pit structure suggest there are two stages in pit development. The first involves the initial dissolution of metal atoms and opening of the pit, and the second involves pit enlargement or growth. For both materials, pits initiate at secondary particles within the metal matrix. In the case of Al 5456 and SiCw/Al 5456, it is shown that these particles are intermetallic phases composed of alloying elements Mg, Cr, Mn, and Al, as well as, Fe, which is an impurity of the metal. Under equivalent conditions of preparation and processing, a greater number of intermetallic phases form in the ...
118 citations
TL;DR: Galvanic interaction between the Al alloys 1100, 2024, 2219, 6061, 7075, and Ag, Cu, Ni, Sn, Cd, Zn, the stainless steels 301, 304L, 347, A286, PH13-8Mo, Steel 4130, Inconel 718, Haynes 188 and Ti-6AI-4V has been studied in air saturated 3.5% NaCl by weight loss measurements and continuous monitoring of the galvanic current in 24 hour tests as discussed by the authors.
Abstract: Galvanic interaction between the Al alloys 1100, 2024, 2219, 6061, 7075, and Ag, Cu, Ni, Sn, Cd, Zn, the stainless steels 301, 304L, 347, A286, PH13-8Mo, Steel 4130, Inconel 718, Haynes 188 and Ti-6AI-4V has been studied in air saturated 3.5% NaCl by weight loss measurements and continuous monitoring of the galvanic current in 24 hour tests. Results show that the potential difference of uncoupled dissimilar metals, while in most cases accurately predicting the direction of current flow, is a poor indicator of the extent (rate) of galvanic corrosion of coupled dissimilar materials. The values of the average galvanic current density agree well with the increase of dissolution rates due to galvanic coupling. In general, galvanic corrosion of Al alloys coupled to dissimilar metals decreases in the order Ag > Cu > steel 4130 ≫ stainless steels ≈ Ni > Inconel 718 ≫ Ti-6AI-4V ≈ Haynes 188 >Sn > Cd. Coupling to zinc does not result in cathodic protection for all Al alloys studied, but can lead to increas...
57 citations