| Description |
xvi, 100 leaves : illustrations ; 29 cm |
| Summary |
"The anodic dissolution of magnesium was studied in MgCl₂-KC1 and MgBr₂-KBr mixtures at 25, 40, and 55 °C. The parameters of the study were current density, concentration of magnesium ion, and temperature. The concentration of magnesium ions was varied from 0.001 to 1 N holding the ionic strength constant at 1.5. The weight loss of magnesium from the electrode during electrolysis was determined by weighing the electrode both before and after electrolysis. The current was measured with a sensitive milliammeter. The range of the current densities was varied from 0.001 to 0.1 amps·cm⁻². The apparent valence of magnesium ions going into solution was determined. The following was concluded: (1) The apparent valence of magnesium dissolving anodically is decreased rapidly as current density is increased at current densities below 0.03 amps·cm⁻². From 0.03 to 0.1 amps·cm⁻², the apparent valence decreases slowly with increasing density. (2) The effect of concentration of magnesium ions and temperature on the apparent valence of magnesium dissolving anodically in KCl-MgCl₂ and KBr-MgBr₂ mixtures is small. (3) The apparent valence of magnesium dissolving in 1 N MgCl₂ and MgBr₂ solutions has a much more pronounced temperature and current density effect at low current densities. (4) The apparent valence-current density plots for the anodic dissolution of magnesium can be separated into two regions where there exists linear relationships between them. The potential measurements of magnesium dissolving anodically under similar conditions led to the following conclusions: (1) The overpotential is very slightly affected by temperature and concentration, except in 1 N MgCl₂ and MgBr₂ solutions. (2) The electrode is not appreciably polarized at current densities below 0.03 amps·cm⁻². Above 0.03amps·cm⁻² the electrode polarizes rapidly indicating passivation. On the basis of the above, it is concluded that the behavior of magnesium is consistent with the model proposed by Sun in which the anodic dissolution consists of three simultaneous processes, an electrochemical reaction, local corrosion, and disintegration. The deviation of the valence of the magnesium ions from the normal valence, i.e., deviation from Faraday's law, is accounted for by local corrosion and disintegration. A mathematical model is derived that gives the observed influence of current density"--Abstract, leaves iii-iv. |
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