MEASUREMENT OF PAINT COATING RESISTANCE IN ELECTROLYTE

The use of known methods for measuring the electrical resistance of a protective coating in an electrolyte is associated with the danger of using high voltage, which accelerates degradation of the coating. The structural diagram of a measuring device operating at a low voltage of up to 1.5 V is substantiated. The device contains two galvanic cells with an electrolyte, a capacitor, a switch, a digital multimeter, and a three-position switch. One galvanic cell is attached to the coating on a carbon steel plate and is equipped with an electrode made of stainless steel. The second galvanic cell is equipped with electrodes made of carbon and stainless steel. It is a source of reference voltage. The input resistance of the multimeter from 1 MOhm serves as a reference resistance. The maximum value of the measured coating resistance reaches 1400 MOhm. A formula is obtained for calculating the specific electrical resistance of the paint and varnish coating in an electrolyte solution. Using the manufactured device, the dynamics of changes in the specific electrical resistance of two coatings made of Raptor polyurethane paint with a hardener are studied. The coatings were applied in two and three layers, the duration of testing in the borofoska solution was 200 days. Upon completion of the tests, the specific electrical resistance of the three-layer coating decreased from 480 to 20 MOhm∙m, it was 4 times greater than the two-layer coating. This result indicates a significant increase in the protective resistance of the polyurethane coating after applying the third layer.