On the Role of Buffers and Anions in NiFe Electrodeposition

Hydrogen evolution and buffering, which are important processes in deposition, have been investigated in solutions containing no Ni2+ or Fe2+ ions. Limiting currents for hydrogen evolution are found to be significantly higher in solutions of Na2SO4 than in NaCl and NaClO4 solutions at the same pH. Boric acid does not act as a buffer during H+ reduction in these systems, but does reduce the overpotential for H2O discharge. The H limiting current is actually decreased in Na2SO4 solutions by addition of is postulated that this molecule can adsorb and decrease the active surface area. In NaCl solutions, H3BO3 has no effect on Citric acid is an effective buffer. Saccharin has little effect on the H overpotential on Ni electrodes, but causes a small concentration-independent increase in il in Cl-- solutions. Boric acid shows no effect linear potential sweep curves during NiFe deposition from Cl-- but addition of H3BO3 substantially increases the current efficiency. Boric acid decreases currents during linear potential sweeps in SO42-- solutions, probably by decreasing the active electrode area through adsorption.36 refs.--AA