Comprehensive Approach to Evaluating Zinc Coating Quality on Pump-Compressor Pipe Couplings Based on Studying Structure and Properties

Use of a protective coating is a promising area for increasing the service life of threaded pipe–coupling connections of pump-compressor pipes during oil recovery. Operating properties of electrolytic, thermal diffusion, and hot zinc coatings on pipe steels 45, 30G2, 37G2F, and 37G2S of different strength groups were studied. Coating thickness, uniformity, microhardness, and wear resistance are determined. It is shown that zinc coatings, depending on application technology, differ with respect to the parameters studied, although values of these indices hardly depend on the metal base. Thermal diffusion coatings have significantly higher hardness compared with hot and electrolytic coatings, and also the best wear resistance. The procedure developed makes it possible to evaluate comprehensively zinc coating quality on couplings to pump-compressor pipes and may serve as a basis for developing standard methods of zinc coating quality evaluation with the aim of further verification of products with this form of coating.