Corrosion of complex electronic equipment is an increasingly serious problem, causing expensive damage. Corrosion occurs through out the entire life cycle during different stages of manufacturing, assembly, transport and storage of components and assemblies and during field operations of the equipment. Presence of moisture, chloride, sulphur dioxide, hydrogen sulphide and other airborne corrosives, meteorological parameters etc influence the occurrence of corrosion. The present review describes the current understanding mechanism of corrosion of electronic components and equipments in different environmental conditions. The various corrosion testing methods and methods of corrosion prevention in these electronic devices have also been elaborated.
Human sweat comes in contact with a number of consumer products. This results in a variety of undesirable effects such as corrosion and malfunction. Corrosion behaviour of three metals, namely, mild steel (MS), galvanized steel (GS) and SS 316 L in artificial sweat (the ISO standard ISO 3160-2) has been studied by polarization study and AC impedance spectra. The study reveals that the decreasing order of corrosion resistance is SS 316 L > MS > GS.
Phosphonic acids are noted for their hydrolytic stability, scale inhibiting property and ability to form complexes with metal cations. Hence they have been widely used as corrosion inhibitors [1][2][3][4][5][6][7][8][9][10][11]. In our earlier study [4], we reported on the synergistic effect of sodium salt of phenyl phosphonic acid (PPA) and Zn 2+ on the corrosion inhibition of mild steel in a neutral aqueous environment containing 60ppm Cl -. It was observed that the formulation consisting of 300ppm PPA and 50ppm Zn 2+ has 95 per cent corrosion inhibition efficiency. The addition of a higher concentration of Zn 2+ decreased inhibition efficiency. The reason for this decrease is investigated in this paper. The inhibition efficiencies of various other PPA-Zn 2+ combinations have also been studied. This study also aims to find out whether phenyl phosphonic acid coordinates with metal cations such as Zn 2+ and Fe 2+ , through the phenyl group or phosphonate group of both, in solution and in solid state. ExperimentalPreparation of the specimens Mild steel specimens (0.02 to 0.03 per cent S; 0.03 to 0.08 per cent P; 0.4 to 0.5 per cent Mn; 0.1 to 0.2 per cent C; and the rest iron) with dimensions of 1 × 4 × 0.2cm were polished to a mirror finish, degreased with trichloroethylene and used for the weight-loss method. Weight-loss methodMild solution specimens, in triplicate, were immersed in 100ml of the solutions containing various concentrations of the inhibitor in the absence and presence of Zn 2+ , for a period of seven days. The weights of the specimens before and after immersion were determined using a Mettler balance AE-240.The UV-visible spectra were recorded using a Hitachi U-3400 spectrophotometer.
The inhibition efficiency of a cationic surfactant, N-cetyl-N,N,Ntrimethyl ammonium bromide (CTAB), in controlling corrosion of carbon steel immersed in 60 ppm CI" has been evaluated by weight loss method. The influence of CTAB on the inhibition efficiencies of several systems has been investigated. CTAB as a monomer accelerates corrosion; but as a micelle it controls corrosion. CTAB, at concentration equal to or greater than critical micelle concentration (CMC) lowers the inhibition efficiencies of some systems like sodium gluconate -Zn 2+ , 2-chloroethylphosphonic acid -Zn 2+ , amino (trimethylene phosphonic acid) -Zn 2+ , l-hydroxyethane-1,1diphosphonic acid-Zn 2+ . CTAB does not alter very much the inhibition efficiencies of some systems such as calcium gluconate, calcium gluconate-Zn 2+ . Zn 2+ improves the inhibition efficiency of CTAB, below its CMC, but decreases the inhibition efficiency of CTAB, above its CMC. CTAB has biocidal activity as a monomer and also as a micelle.
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