IMPROVING THE PROTECTIVE PROPERTIES OF PAINT AND VARNISH COATINGS

.To control the ionic permeability of coatings for the purpose of increasing the corrosion, water, and moisture resistance compounds of various classes, in particular oil-soluble sulfonates, a mixture of saturated and unsaturated fatty acids, and sulfur- and phosphoruscontaining substances, have been added to the composition of paint and varnish materials. In selecting inhibltors their combinability with film formers was taken into consideration and also their water solubility so that in the case of penetration of the electrolyte through the film the inhibitor concentration remains constant for a long time. The experiments were made on GF-020 and GF-017 glyptal primers, which are widely used in the automobile industry. The inhibiting substances were added directly to the primer compositions, which were previously brought to the working viscosity (from 18 to 30 sec using a VZ-4 viscosity gauge), and carefully mixed. The adhesion strength of the coatings was established by the lattice incisions method (All-Union State Standard 15140-69) and the hardness was measured on a pendulum instrument (A11-Unlon State Standard 5233-67). The elastlcity, i.e., the strength of the film in bending (A11-Unlon-State Standard 6806-73) and the strength of the coatings in impact on a UI-A instrument (All-Union State Standard 4765-73) were also determined. The anticorroslon properties were determined from the resistance of the coating to the action of distilled water and salt solutions (All'Unlon State Standard 21065-75), from the resistance of the coating in a heat and humidity chamber at 50 ~ 5~ and 80-1009 humidity , and also from the active and reactive components of impedance at the sample--electrolyte boundary established by an accelerated method. Known similar methods [2, 3] are based on the fact that in essence corrosion processes occurring under a polymer coating are electrochemical and their rate depends upon the rate of diffusion of water and oxygen through the coating, the ionic permeability of the coating, its swelling, etc. These properties, in turn, are determined by the quality of the protective film, its structure, the presence in the polymer of functional groups, the capacity for electroosmosls, the ion-exchange properties, and other factors. The impedance measurements were made with the use of an R-568 ac bridge with a signal frequency of I0 kHz, an ac voltage amplitude of not more than 5 mV, a sensitivity of 40 dB, and a temperature of 20~ in a 39 sodium chloride solution. The auxiliary electrode was a cylindrical platinum grid, the total area of which was hundreds of times grea~er than the area of the working electrode.