BACKGROUND: The paper presents the results of research into new protective coatings for marine structures in tropical climates. The studies were conducted within the framework of the scientific research project «Ecolan T-1.1, Task 9», implemented with the support of Joint Vietnam-Russia Tropical Science and Technology Research Center. This work is integrated into the center’s comprehensive scientific agenda and aims to address pressing challenges in the field of material protection under tropical conditions. The main focus was on studying the impact of the marine environment on galvanized steel and the effectiveness of coatings modified with biocidal additives. A protective system based on electrochemical galvanizing with a biocidal component has been developed. Marine testing conducted in the waters of the East Sea (Khanh Hoa, Viet Nam) demonstrated an 80% reduction in biofouling and high corrosion resistance of the coatings. The obtained results demonstrate the promising potential of applying the developed compositions for protecting ship structures. The findings provide a scientific basis for further development and implementation of environmentally friendly protective coatings in marine engineering and tropical construction applications. The study investigates the development of environmentally friendly anti-corrosion coatings for offshore structures. There’s a need to replace toxic biocidal compounds with safe alternatives due to the high biofouling rate in the coastal zone of tropical seas. AIM: To study the performance of zinc coatings with organic additive compounds to protect steel structures from biofouling and corrosion in the marine environment. METHODS: The study used: St3 steel samples measuring 175×250×3 mm; sulfate electrolyte for galvanizing with zinc sulfate concentration of 200–300 g/l; zinc coatings with addition of organic compounds (OC 1–4). The methodology of marine testing in the East Sea (Khanh Hoa, Viet Nam); microscopic analysis; iodometric titration; gravimetric method for determining the corrosion rate. RESULTS: The research has shown a significant reduction in biofouling and corrosion on samples with biocidal additives. Control samples were characterized by intensive formation of marine organism colonies, while samples with additives maintained surface integrity. The corrosion rate decreased by 50%, with maximum protection (61%) achieved using OS 4 (1 mmol/L, 1 A/dm²). The growth of sulfate-reducing bacteria was suppressed: the latent period was 48 hours, and the life cycle of Desulfovibrio was 7 days. The concentration of biogenic hydrogen sulfide decreased significantly. Zinc coatings with additives formed a dense structure with reduced permeability. The developed coatings represent a promising environmentally friendly alternative to traditional antifouling compounds while maintaining the functionality of structures in a marine environment. The economic efficiency was confirmed by the use of St3 steel. CONCLUSION: The developed coatings with organic additives provide effective protection of steel structures from biofouling and corrosion in the marine environment. The findings may be used to develop new anti-corrosion materials for marine equipment and structures and ensure their long-term operation under intensive biofouling conditions. The issue of ship structure protection from biofouling in tropical waters is of particular importance due to the high colonization intensity of underwater surfaces by marine organisms in the coastal zone of Viet Nam. Existing protective systems do not show the required performance in corrosive marine environments, necessitating the development of new high-performance composite solutions.

The study is based on the study of the effect of an organic compound (OC) - hydrocinnamic (3-phenylpropanoic) acid on the bacterial cells of SRB (sulfate-reducing bacteria), which are stimulants of corrosion processes. Selection of conditions of use and a quantitative assessment of the effectiveness of the inhibitory (biocidal) action of the studied OC, which can be used to protect steel from corrosion in environments containing SRB. In the course of the study, the effect of OC on the development of SRB was studied and such parameters as the change in the pH value and the redox potential of the samples in the medium, the number of bacteria and the content of biogenic hydrogen sulfide depending on the concentration of the used OC were determined. The main conclusions are drawn about the inhibitory corrosion and biocidal actions of the test OC by assessing the corrosion rate of steel samples and the protective effect depending on the selected concentrations of the OC by gravimetry. An additional assessment of the inhibitory effect was carried out by the method of electrochemical impedance spectroscopy and by the method of taking the polarization curves of the test samples.

The article investigated the creation of a composite electrochemical coating (CEC) zinc-inhibitor with the inclusion of an organic compound (OC) with biocidal and inhibitory effects, which can be used to protect steel from corrosion in environments containing sulfate-reducing bacteria (SRB). The coating was applied to steel by electrochemical deposition. The OC was turned on by modifying the zinc sulfate electrolyte. The evaluation of the protective effect of CEC against microbiological corrosion was carried out during a laboratory study of samples with coatings placed in a Postgate "B" inoculated SRB medium for 7 days. In the course of the study, such parameters as changes in the electrode potential of samples in the medium, hydrogen index and redox potential of the medium, concentrations of bacterial cells and biogenic hydrogen sulfide were determined. At the end of the tests, the corrosion rate and the protective effect of the coating by the gravimetric method were determined. Evaluation of the inhibitory effect was carried out by electrochemical impedance spectroscopy and polarization curves of samples with CEC, exposed for 7 days in inoculated SRB nutrient medium Postgate "B". The study found: improvement of the coating structure due to the introduction of OC, the biocidal and inhibitory effects of CEC, a decrease in the corrosion rate of CEC by about 2 times with respect to the zinc coating.