A calcareous deposit is a by-product of the cathodic polarization in seawater environments. This study presents the results of evaluating the anticorrosion and anti-macro-biofouling effectiveness of a calcareous deposit layer on the surface of the cathodically polarized AH36 structural steel in tropical seawater. The polarization is induced with initial current densities at which the calcareous deposit layer formed with both aragonite and brucite for 12 months continuously. The protective properties of the layer were compared with those of the passive layer from corrosion products under the same environmental conditions. The macro-biofouling in the tropical seawater is observed in the closed and open surfaces of the steel. The comparison of the anticorrosion property shows that, to some degree, the calcareous deposit layer contributes to surface passivation, as in the case of the corrosion product layer. In addition, the composition of the brucite and aragonite in the calcareous layer in the study plays a role as a macro-biofouling growth-limiting factor.

Studies have been carried out to evaluate the effect of chromium carbide on the corrosion resistance of coatings obtained by plasma heating of mixtures of NiCrBSi alloy powder and OK 84.78 coating on the surface of St3 steel. It has been established that an increase in the content of chromium carbide in the initial composition of the coating leads to an increase in the microhardness of the modification coatings, but at the same time, the likelihood of cracks and pores also increases. An increase in the content of chromium carbide in the composition of the coating affects the mechanism of formation of the grain structure of the surface layer. Studies of coating corrosion in 3% NaCl solution showed that, with an increase in the chromium content in the coating composition, the corrosion potential decreases, while corrosion current density increases with an increase in carbon content.