STRUCTURE FORMATION OF Ni−P ALLOY ELECTROCOATINGS WITH INCREASED CORROSION RESISTANCE

Purpose of research. The main factors that reduce the protective properties of electrocrystallized coatings are the formation of volumetric defects − pores, as well as the occurrence of microgalvanic couples at grain boundaries, that is, on surface defects of the crystalline structure. Creating a non-porous structure in electrocoatings, eliminating the formation of surface defects in metal/alloy layers, as well as the possibility of replacing chromium coatings, which are obtained from toxic electrolytes, are urgent tasks. Materials and methodology. In the work, it was proposed to use electrocoatings with Ni−P alloy as protective layers on products that increase corrosion resistance. An X-ray determination of the phase composition of Ni−P electrochemical deposits was carried out. The surface morphology and corrosion resistance of coatings were studied. Results. Samples of electrochemical coatings of pure nickel and nickel-phosphorus alloy were studied. It has been established that during the formation of nickel coatings with the addition of phosphorus ions, the surface morphology has practically no pores, amorphization of deposits occurs, due to which the protective properties, namely, corrosion resistance, are improved. Scientific novelty. Factors have been identified that influence the increase in corrosion resistance of coatings − the absence of a porous structure and the formation of an amorphous state. Conclusions. The influence on the structure and properties of electrochemical coatings of a nickel-phosphorus alloy has been studied. It has been established that the addition of phosphorus ions to the nickel plating electrolyte leads to the formation of an amorphous structure in the coatings, and layers of the Ni−P alloy appear practically without the presence of pores. It has been established that the effect of increasing the corrosion resistance of the electrochemical coating with a nickel-phosphorus alloy (by 30 %) is due to the formation of an amorphous structure of the solidifying metal liquid while preventing the crystallization process during electrochemical deposition.