The results of testing sets of samples of a nipple coupling with a threaded connection NC-50 (4 ½ IF) of API 7 standard of pipes made of X 3 MnCrNiMoN 20 13 steel with a wear-resistant mineral coating and without coating are presented. A set of samples of a nipple-coupling pipe made of X 3 MnCrNiMoN 20 13 steel with a wear-resistant mineral coating successfully withstood the planned number of screwing and unscrewing cycles (400 cycles), which is more than an order of magnitude more than a set of samples of this steel without mineral coating (30 cycles). The predicted number of cycles of screwing and unscrewing this pair is not less than 1000.