The galvanic corrosion theory of adherence between ground‐coat enamels and steel was investigated as a part of a broad study of the bonding mechanism between ceramics and metals. The theory, which is outlined in this report, is based on the mechanical anchoring of the enamel into the pits formed by the galvanic attack of the enamel on the steel surface. The theory was first examined from the standpoint of the data on adherence obtained in earlier studies at the National Bureau of Standards. In addition, several experiments were performed which demonstrated that galvanic corrosion of the metal base could occur during the short firing times encountered in enamel processing. On the other hand, certain inconsistencies were observed in the data which indicated that the mechanism of galvanic attack followed by mechanical anchoring was not the only important factor affecting the bond strength.

SUMMARYAn investigation was made of the effects of (a) the firing time and (b) the weight of nickel deposited frm the nickel-dip solution on the adherence developed by a cobalt-free and a cobalt-bearing ground-coat enamel on both enameling iron and a titsmim-bearing low-csrbon steel. At 1550°F it was found that the maximum benefit from the nickel on the measured adherence index occurred at 2-minute firing. The effect of the nickel, however, dropped markedly with longer firing times. It was also found that there was an optimum nickel deposit for maximum adherence. This optimum varied from 50 to about 120 milligrams per square foot, depending on the type of cleaning used and the type of enamel applied.It was found that the nickel dip reduced the tendency toward fishscaling. Furthermore, there appeared to be a relation between fishscaling resistance and good adherence; no spec~en with~a~erence~dex of 70 .or over showed fishscaling tendencies.Metallographic studies of the interface of coated specimens showed .that nickel dipping of the steel prior to enameling brought about a surface roughening during the firing operation. A relation ms noted between the degree of roughetig and the measured adherence index. The roughening of the steel surface was ascribed to galvanic corrosion.

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The functions of the National Bureau of Standards are set forth in the Act of Congress, March 3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and maintenance of the national standards of measurement and the provision of means and methods for making measurements consistent with these standards; the determination of physical constants; and properties of materials; the development of methods and instruments for testing materials, devices, and structures; advisory services to government agencies on scientific and technical problems; inven tion and development of devices to serve special needs of the Government; and the development of standard practices, codes, and specifications. The work includes baric and applied research, develop ment, engineering, instrumentation, testing, evaluation, calibration services, and various consultation and information services. Research projects are also performed for other government agencies when the work relates to and supplements the basic program of the Bureau or when the Bureau's unique competence is required. The scope of activities is suggested by the listing of divisions and sections on the inside of the back cover, PublicationsThe results of the Bureau's work take the form of either actual equipment and devices or pub lished papers. These papers appear either in the Bureau's own series of publications or in the journals of professional and scientific societies* Hie Bureau itself publishes three periodicals available from the Government Printing Office: The Journal of Research, published in four separate sections, presents complete scientific and technical papers; the Technical News Bulletin presents summary and preliminary reports on work in progress; and Baric Radio Propagation Predictions provides data for determining the best frequencies to use for radio communications throughout the world. ForewordReliable data on the mechanical properties of structural materials at high temperatures are of critical importance in the development of aircraft engines, aircraft and missile frames subject to aerodynamic heating, and certain types of nuclear reactors. The measurement of strain in such structures not only pro vides the engineer with knowledge of the performance characteristics of the structure, but also gives information for improving the design.This Monograph summarizes work done at the National Bureau of Stand ards in a research program aimed at the development of new types of strain gages for high-temperature use. Sponsored by the Navy and the Air Force, the program has included an investigation of the properties of high-temperature strain-gage materials, the development of high-temperature strain gages, and the development and evaluation of high-temperature strain-gage cements.In discussing properties of strain-gage materials, it has been necessary to use proprietary names in referring to some of these materials. However, it should be understood that the Bureau does not recommend nor endorse any of the proprietary products mentioned...

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