This memorandum, constitutes a report on the results of experiments conducted at the U. S. Waterways Experiment Station on a small scale model of that reach of the Mississippi River near and including Dogtooth Bend (Mile 32.7 above to Mile 4.0 below Cairo).

"An investigation of the corrosion of light metal alloys used in aircraft was begun at the National Bureau of Standards in 1925 and has for its purpose causes of corrosion in aluminum-rich and magnesium-rich alloys together with the development of methods for its prevention. The results, obtained in an extensive series of laboratory and weather-exposure tests, reveal the relative durability of a number of commercially available materials and the extent to which the application of various surface coatings of oxide alone and with paint coatings afforded additional protection. The paper may be considered as a supplement to NACA report 490" (p. 395).