The dependence of the anomalous codeposition of iron‐nickel alloys on the pH at the cathode surface is investigated. An equation is derived to evaluate the surface pH as a function of bulk pH, rate of hydrogen evolution, buffer concentration, and diffusion conditions. The results obtained on rotating disk electrodes show that anomalous codeposition is due to a suppression of nickel discharge and that suppression occurs only when the surface pH is high enough to cause hydroxide formation. A type of mechanism is proposed by which the adsorption of ferrous hydroxide suppresses the deposition of nickel but permits a high rate of iron discharge. Experimental results which support this mechanism are discussed. This type of mechanism could be of general importance for other systems exhibiting anomalous codeposition.

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A new bath for the electrodeposition of Ni‐Fe‐Cr magnetic thin films has been developed. The bath is similar to a typical Permalloy electrodeposition bath, being modified only by the addition of 0.020M chromic chloride and 0.10M acetic acid. Deposits with up to 8 weight percent Cr were produced; the chromium content of the deposit increased with increasing current density. Current efficiencies of up to 50% were attained when at least one‐half of the chromium in the bath was present as Cr2+. The acetic acid serves to limit the precipitation of nonmetallic material on the electrode by forming a soluble complex with Cr3+ and/or by buffering the pH at the electrode surface. The incorporation of chromium into the deposit is limited by the reduction rate of Cr2+ to Cr0.

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