The structural features of the porous type of anodic oxide coating applied to aluminum have been investigated with the electron microscope. These coatings consist of close‐packed cells of oxide, predominately hexagonal in shape, each of which contains a single pore. Pore size is a function of the electrolyte used and is independent of forming voltage. Wall thickness and barrier thickness are primarily a function of forming voltage and are affected to a minor degree by the electrolyte type. Pertinent dimensions of anodic coatings formed in sulfuric acid, oxalic acid, chromic acid, and phosphoric acid electrolytes are presented, and formulas are given for calculating the cell size and pore volume of these coatings.
A novel method is described for measuring the thickness of a barrier typ~ anodic oxide coating or the barrier layer portion of a porous type anodic oxide coating. This method is used to follow the evolution of the barrier layer during the early stages of the formation of a porous type coating on aluminum and to establish certain dimensions of the fundamental oxide cells which comprise this type of coating.
corrosion temperature is very close to the maximum temperature of the cycle.
CONCLUSIONSThe linear corrosion rate of Zircaloy-2 which occurs at very long exposure times at low temperatures can be determined in a relatively short time by measurement of the corrosion rate at the low temperature in question after sufficient previous exposure at a higher temperature to reach the linear portion of the weight gain-time curve. This technique should be applicable to other alloys of the Zircaloy type.The transient effects which persist for a time after a change of temperature has been effected are discussed in terms of several aspects of corrosion mechanism. No completely satisfactory explanation of this behavior is offered.
Letter to the editorEffective population size remains a suitable, pragmatic indicator of genetic diversity for all species, including forest trees Disclaimer This correspondence does not represent the official finding or policy of any government or institution but only the authors' opinion. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the United States Government or any government.
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