INFLUENCE OF ANODE MATERIAL ON CURRENT YIELDS DURING FERRATE(VI) PRODUCTION BY ANODIC IRON DISSOLUTION .1. CURRENT EFFICIENCY DURING ANODIC-DISSOLUTION OF GREY CAST-IRON TO FERRATE(VI) IN CONCENTRATED ALKALI HYDROXIDE SOLUTIONS

Current efficiency for the oxidation of a grey cast iron anode to ferr ate(VI) in 14M NaOH was measured in the region of bubble induced conve ction. The maximum current yield, obtained after 180 min of electrolys is, had a value of 11% at a current density of 32 mA cm(-2) and a temp erature of 20 degrees C. The ferrate(VI) current yield increased throu ghout the whole current density range under study (from 1 to 36 mA cm( -2)). The iron anode was activated by cathodic prepolarization. The ir on concentration in lower oxidation states in the solution after elect rolysis was constant within experimental error over the whole temperat ure range under study. The quasisteady state anodic polarization curve for grey cast iron in the transpassive potential region was measured. This anodic polarization curve was shifted to more negative potential , at the same current density, compared to the potential of the mild s teel anode.