ALBERT

Notes: A simplified analysis is presented to describe diffusion and trapping of atomic hydrogen in crystalline silicon. Predictions of the rate of advancement of the trapped hydrogen front as a function of process and material variables are obtained from a numerical solution of the transport equations. We demonstrate that the solutions are compatible with data on boron passivation at 150 °C only when the diffusivities obtained by extrapolation from the high-temperature results of Van Wieringen and Warmoltz [Physica 22, 849 (1956)] are used to represent atomic hydrogen diffusion in the absence of trapping.

Notes: The inhibition efficiency of sodium gluconate (SG) in controlling corrosion of carbon steel immersed in the environment containing 60 ppm Cl– has been evaluated in the presence and absence of Zn2+ by weight loss method. SG and Zn2+ show a synergistic effect. The protective film has been analysed by FTIR and fluorescence spectra. The protective film consists of Fe2+-gluconate complex and Zn(OH)2. The film is found to be UV-fluorescent. The IE of the SG-Zn2+ system increases in the presence of Na2SO4; but decreases in the presence of Na2SO3 and also in the presence of N-cetyl-N,N,N-trimethyl ammonium bromide. This study reveals that the transporting phenomenon plays a larger role than the scavenging of dissolved oxygen.

Notes: Purpose - To evaluate the inhibition efficiency (IE) of polyvinyl alcohol (PVA) in controlling the corrosion of carbon steel immersed in neutral aqueous solutions containing 60?ppm of Cl-, in the absence and presence of Zn2+. To investigate the influence of sodium sulphite (Na2SO3), sodium dodecyl sulphate (SDS), pH and duration of immersion on the IE of PVA-Zn2+ system. To analyse the protective film formed on the metal surface. Design/methodology/approach - The IE has been evaluated by weight loss method. The protective film was analysed by FTIR and fluorescence spectra. Findings - A formulation consisting of 100?ppm of PVA and 75?ppm of Zn2+ offered 81 per cent IE to carbon steel immersed in a solution containing 60?ppm of Cl-. A synergistic effect on inhibition of a combination of PVA and Zn2+ was observed during the tests. The protective film consisted of the Fe2+-PVA complex and Zn(OH)2. It was found to be UV-fluorescent. When SDS was added to the PVA-Zn2+ system, the mixture showed maximum IE at the critical micelle concentration (200?ppm) of SDS (an anionic surfactant). The oxygen-scavenging effect of Na2SO3 increased as the concentration of Na2SO3 was increased. At lower concentrations of Na2SO3, the transport of the inhibitors played a more major role than did the removal of dissolved oxygen. As the pH value was increased, the IE of the PVA-Zn2+ system decreased. As the duration of immersion was increased, the IE was observed to decrease. Research limitations/implications - Electrochemical studies such as polarization and AC impedance spectra will enlighten more on the mechanistic aspects of corrosion inhibition. Practical implications - If this study is carried out at high temperature under simulated conditions, the findings may find applications in cooling water systems. Originality/value - The role of transport of inhibitors towards the metal surface from the bulk of the solution, formation of micelles by surfactants, removal of dissolved oxygen by oxygen scavenger, competition between formation of insoluble iron-inhibitor complex on metal surface and formation of soluble iron chloride in influencing the inhibitive property has been investigated. The protective film was analysed by FTIR spectra and fluorescence spectra.

Notes: The influence of a cationic surfactant, N-cetyl-N, N, N-trimethyl ammonium bromide (CTAB) on the inhibition efficiency (IE) of calcium gluconate (CG) - Zn2+ system in controlling corrosion of mild steel in a neutral aqueous environment containing 60ppm Cl- has been evaluated by weight-loss method. The formulation consisting of 200 ppm CG and 50ppm Zn2+ has 86 per cent IE (immersion period = three days). Addition of various concentrations of CTAB to the above system improves the IE to 99 per cent. Presence of CTAB facilitates the transport of CG and Zn2+ from the bulk of the solution to the metal surface. The nature of the protective film formed on the surface of mild steel has been analysed by FTIR and fluorescence spectra. The protective film is found to be fluorescent and to consist of iron-CG complex, iron-CTAB complex and Zn(OH)2.

Notes: The corrosion rates of mild steel in a neutral aqueous environment containing 60 ppm C1- in the absence and presence of the sodium salt of amino (trimethylene phosphonic acid) (ATMP), polyacrylamide (PAA) and Zn2+ have been evaluated by the classical weight-loss method. The formulation consisting of 50 ppm PAA and 50 ppm Zn2+ and also the ATMP (300 ppm) -ZN2+ (50 ppm) system shows synergistic effect while the formulation consisting of 300 ppm ATMP and 50 ppm PAA shows antagonistic effect. The formulation consisting of 300 ppm ATMP, 50 ppm Zn2+ and 50 ppm PAA has 98 per cent corrosion inhibition efficiency and 99.9 per cent biocidal efficiency. The mechanistic aspects of corrosion inhibition are based, in a holistic way, on the results obtained from potentiostatic polarization study, X-ray diffraction technique, UV-visible, FTIR and luminescence spectra. Found that the protective film consists of FE2+-ATMP complex, Fe2+-PAA complex and Zn(OH)2.

Notes: Phosphonates have shown synergistic effects in combination with Zn2+ ions in controlling the corrosion of carbon steel immersed in neutral aqueous environments containing 60-ppm Cl-. The role of phosphonates in the presence of Zn2+ ions has been investigated by polarisation tests and weight loss results. It was observed that the phosphonates functioned as transporters of Zn2+ ions from the bulk of the solution towards the metal surface. The phosphonate-Zn2+ bond is sufficiently strong to carry Zn2+ ions from the bulk solution towards the metal surface, but is weak enough for them to break to form a phosphonate-Fe2+ bond at anodic sites on the metal surface. Inhibition efficiency increases when the phosphonate-Zn2+ complex remains in solution in soluble form. Inhibition efficiency decreased when the phosphonate-Zn2+ complex was precipitated in the bulk of the solution.

Notes: The formulation consisting of 300ppm 1-hydroxyethane-1, 1-diphosphonic acid (HEDP), 50ppm polyacrylamide (PAA) and 50 ppm Zn2+ offered 99 per cent corrosion inhibition and 99 to 99.9 per cent biocidal inhibition to mild steel in neutral aqueous environment containing 60ppm Cl- , a situation commonly encountered in cooling water systems. The nature of the protective film formed on the metal surface was analysed using X-ray diffraction, UV-visible reflectance, FTIR and luminescence spectra. The film was found to be luminescent and to consist of Fe2+ -HEDP complex, Fe2+ -PAA complex and Zn(OH)2.

Notes: The inhibition efficiency of the formulation consisting of 1-hydroxyethane-1, 1-diphosphonic acid (HEDP), molybdate and Zn2+ in controlling the corrosion of mild steel in neutral aqueous environment containing 60ppm Cl- has been evaluated by the weight-loss method. The formulation consisting of 50ppm HEDP, 300ppm molybdate and 10ppm Zn2+ has 97 per cent inhibition efficiency. The nature of the protective film has been analysed by using x-ray diffraction (XRD), FTIR and fluorescence spectra. The protective film is found to be fluorescent and to consist of Fe2+-HEDP complex, Fe2(MoO4)3 complex and Zn(OH)2. A suitable mechanism of corrosion inhibition is proposed based on the results obtained from the weight-loss method, polarisation study, XRD, FTIR, fluorescence and atomic absorption spectra.