No abstract

The current flow for a local electrolytic cell with rectangular anode and cathode is calculated as a function of a polarization parameter, electrolyte thickness and conductivity, anode and cathode size, and zero current potential difference. The total current is obtained from the numerical computation (with error analysis) of a series solution of Laplace's equation assuming a linear polarization relation at the electrode-electrolyte interface. For high values of the polarization parameter and sufficiently thick electrolytes an asymptotic formula obtains for the current approximately proportional to the anodic fraction, as was found by Waber et al. However, in general the cell geometry greatly influences the amount of current flow, especially for anode shapes near to linear rather than near to square. This effect can be greater than an order of magnitude. The calculated results are compared with experimental data obtained by Ogburn and Schlissel and are shown to be in good agreement. Corrosion currents in randomly pitted surfaces may be estimated from the above results.

Electrodeposited lead dendrites were grown and examined by x-ray diffraction and metallographically. Their structure was essentially that of two crystals having a twist relation about a common [111] pole which was normal to the flat surface of the two-dimensional dendrites. Each dendrite contained many small voids or channels. The direction of growth was either about halfway between a <211> direction of one crystal and a neighboring <211> direction of the second crystal or halfway between <110> directions.Electrodeposited dendrites 2 have been described and reviewed extensively by Wranglen (1). He examined dendrites of lead, tin, silver, cadmium, and copper microscopically and by x-ray diffraction and described them as single crystals. Faust and Johns (2) examined electrodeposited dendrites of lead, silver, copper, gold, and aluminum, and by metallography found at least one grain boundary in each of the dendrites growing in <211> or direction.The lead dendrites, as shown by Wranglen, are of two main types: those that are flat and growing in a direction and those that are three dimensional and growing in a <100> direction. The growth of dendrites is favored by conditions of solution depletion, and they are branched at right angles. The dendrites have been described as monocrystalline, branched at 60 ~ , and growing with the plane of the dendrite parallel to a {lll} plane. The lead dendrites examined by Faust and Johns were of the <110> type with "twin planes."As part of a program of investigating the growth and character of metal crystals grown by electrodeposition, we had occasion to grow and examine some lead dendrites. We had hoped to use these as seeds for growing larger crystals, and we wished to know something about the quality of the crystals. Wranglen had considered only morphology and x-ray diffractometer measurements, and Faust and Johns had made only a very limited metallographic examination. All in all very little was known about the lead dendrites which are extremely easy to grow.We grew numerous dendrites of lead by electrodeposition. In many respects they appeared to be the <110> dendrites of Wrang]en, but were neither twinned in the usual sense nor single crystals. The apparent difference is probably attributable to the use of more powerful tools for their examination. Certainly these were not unusual growths inasmuch as they were obtained consistently and to the virtual exclusion of other types. Growth of DendritesThe dendrites were grown by electrodeposition in a 0.5M solution of lead acetate and 2M ammonium acetate with a lead anode and cathode. Reagent grade chemicals and distilled water were used without any purification steps.The plating cell consisted of a 100 ml beaker filled with electrolyte and covered with a rubber stopper. The lead anode was supported at one side of the beaker through a hole in the stopper. On the other side, a glass tube 4 mm in diameter, was inserted in a hole in the stopper and positioned so...

Isolated faces of copper single crystals were plated with copper from copper sulfate‐sulfuric acid solutions. Deposits on {100} and {110} faces, despite the presence of grain boundaries, gave x‐ray diffraction patterns showing uniform lattice orientation. The grain boundaries were associated with topographic features of the deposits. Over‐all metal distribution showed a tendency to deviate from that of poly crystal deposits on polycrystalline bases.

not Available.