Ispitivanje prevlaka Zn-Co legura dobijenih pulsirajućom strujom

The electrochemical deposition by pulse current of Zn-Co alloy coatings on steel was examined, with the aim to find out whether pulse plating could produce alloys that could offer a better corrosion protection. The influence of on-time and the average current density on the cathodic current efficiency, coating morphology, surface roughness and corrosion stability in 3% NaCl was examined. At the same Ton/Toff ratio the current efficiency was insignificantly smaller for deposition at higher average current density. It was shown that, depending on the on-time, pulse plating could produce more homogenous alloy coatings with finer morphology, as compared to deposits obtained by direct current. The surface roughness was the greatest for Zn-Co alloy coatings deposited with direct current, as compared with alloy coatings deposited with pulse current, for both examined average current densities. It was also shown that Zn-Co alloy coatings deposited by pulse current could increase the corrosion stability of Zn-Co alloy coatings on steel. Namely, alloy coatings deposited with pulse current showed higher corrosion stability, as compared with alloy coatings deposited with direct current, for almost all examined cathodic times, Ton. Alloy coatings deposited at higher average current density showed greater corrosion stability as compared with coatings deposited by pulse current at smaller average current density. It was shown that deposits obtained with pulse current and cathodic time of 10 ms had the poorest corrosion stability, for both investigated average deposition current density. Among all investigated alloy coatings the highest corrosion stability was obtained for Zn-Co alloy coatings deposited with pulsed current at higher average current density (jav = 4 A dm-2).Ispitivano je elektrohemijsko taloženje cink-kobalt legure pulsirajućom strujom na čeliku, a s ciljem dobijanja zaštitnih prevlaka sa povećanom korozionom stabilnošću. Prevlake legura su taložene pulsirajućim režimom sa različitim srednjim gustinama struje i pri različitom trajanju katodnog pulsa. Analiziran je uticaj ovih parametara na iskorišćenje struje prilikom elektrohemijskog taloženja na izgled prevlaka (snimanje elektronskim mikroskopom), hrapavost prevlaka i njihovu korozionu stabilnost u 3% NaCl (merenjem slobodnog korozionog potencijala u agensu korozije i snimanjem polarizacionih krivih). Pokazano je da u zavisnosti od vremena pulsa, prevlake taložene pulsirajućim režimom mogu da imaju bolju homogenost, sitnije aglomerate kristalnih zrna i manju hrapavost od onih taloženih pri istim uslovima, ali konstantnom gustinom struje. Veću korozionu stabilnost pokazale su prevlake legura taložene većom srednjom gustinom struje