Influence of the inhibitor treatment on the corrosion resistance of different zones of welded joints
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INFLUENCE OF THE INHIBITOR TREATMENT ON THE CORROSION RESISTANCE OF DIFFERENT ZONES OF WELDED JOINTS Z. V. Slobodyan,1 V. I. Kyryliv,1 L. A. Mahlatyuk,1, 2 and R. B. Kupovych 1
UDC 621.787: 620.176.16; 620.197.3
It is well known that the transition zone is the weakest link of welded joints operating in contact with corrosive media and subjected to the influence of mechanical loads [1]. Numerous researchers observed the electrochemical inhomogeneity of the surface in the base-metal–transition (heat-affected) zone–weld region [2]. It is clear that the indicated heterogeneity leads to the formation different corrosion rates in different zones of the welded joint. Although these rates are largely determined by the mutual influence of these zones, it is of interest to estimate the corrosion resistance of each zone separately. It is well known that the corrosion resistance of a metal can be significantly improved by modifying its surface with special corrosion inhibitors capable of the formation of quasiamorphous layers on the surface [3]. However, the data on the influence of inhibitors on different regions of the welded joint are absent. The metal surface undergoes certain changes as a result of mechanical pulsed treatment (MPT) [4]. In [5], Babei proposed to combine these two methods in order to improve the corrosion-mechanical and corrosion characteristics of steels in acid media. However, the conclusions concerning the behavior of corrosion resistance were made on the basis of the data of electrochemical investigations but not according to the data of direct corrosion tests, which do not allow us to perform their quantitative assessment. The aim of the present work is to study the corrosion resistance of different zones of welded joints in neutral media, including the inhibited media, and after MPT. Materials and Methods The welded joint was made of two strips of 10 steel 6 × 50 × 250 mm in sizes. The edges 3 mm in width were beveled on two sides of the strips (250 mm). A double-sided bead butt weld was made semiautomatically with a 08sv electrode (GOST 2246-70) [6]. The samples 6 × 95 × 100 cm in sizes were cut out from the plate obtained as a result. One side of each sample was subjected to MPT. The welds were cleaned with a grinding wheel and then ground in an updated SPS-20 flat-grinding machine with a tool made of 40Kh steel in a special working medium for carburizing [7] in the following modes: for a linear speed of the hardening tool of 50 m / sec and for a speed of the table of grinding machine of 2 m / min. As a result of treatment, we observe the formation of nanocrystalline layers with a thickness of 150–200 μm and the levels of microhardness near the surface varying from 3 to 5 GPa [4]. Then the transverse strips 6 mm in width were cut out separately from the weld, the transition zone, and the base metal. The transition zone and the weld were determined metallographically [8]. The the well-known Korsol composition [9] with a concentration of 0.2 g / dm3 was used as an inhibitor. The heterogeneity of th
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