The effect of pulsing the current on the composition, the internal stress, and mechanical properties of Ni‐Mo electrodeposits was investigated. The molybdenum, content increased with increasing peak current density and to a lesser degree with decreasing duty cycle. A reduction in the internal stresses was explained in terms of the relaxation of those due to crystallite or fine grain coalescence during the off‐time and an expansion of the surface layer when hydrogen diffused into it at the start of each on‐time. The mechanical properties were improved by high frequency pulse plating. Deposits consisting of alternate layers of different composition annealed at 300°C exhibited further improvement of their mechanical properties.

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Nickel electrodeposits, of various thicknesses, were prepared from Watts' baths containing several addition agents to study the development of the surface structure. By electron‐microscopic examinations of replicas, thin films, and electrolytically thinned bulk metal the reasons for the formation of several structural features, previously observed, were found. Selected‐area diffraction was found to be the best method of measuring the grain size of the electrodeposits studied. Markings believed to be sites of lattice‐included foreign substances were observed.

Nickel deposits of various brightnesses were plated from Watts baths containing several different addition agents. The as-plated surfaces of the deposits were examined by electron microscopy. All bright deposits had a very fine-grained structure. However, some fine-grained deposits showed surface crevices and were therefore not bright. A linear relationship between the fraction of the surface area having a roughness less than 0.15/~ and the logarithm of light reflected as measured with a photocell was found. There is no direct relationship between the degree of preferred orientation and brightness, but the fiber axis is related to the type of structure observed, i.e., platelet, equiaxed crystallite, or spiral-type, and the addition agents in the plating bath.

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