„Ochrona przed Korozją” (Corrosion Protection) No 9/2019
The new generation of anticorrosive zinc primers with improved protective, utility and ecological properties
Sieć Badawcza Łukasiewicz – Instytut Inżynierii Materiałów Polimerowych i Barwników, Oddział Farb i Tworzyw, Gliwice
Instytut Badawczy Dróg i Mostów, Warszawa
The most common coating systems used for long-term corrosion protection of steel structures consist of primer, intermediate and top-coat. Since the performance of sacrificial coatings is based on transfer of galvanic current, which implies metallic contact between the individual active pigments, such coatings are typically very highly pigmented (more than 80% of Zn in dry coating), which sometimes causes losses in cohesive strength and in resistance to impacts. Therefore – and because Zn is known to be harmful to the environment and becoming a rare chemical element – research aims at Zn primers with reduced Zn content and/or even better long time performance. The epoxy primers with different Zn pigments were developed with concentration of zinc particles reduced to about 50% in dry coating. As Zn pigments were used: mixtures of zinc pigments with different particle shape and/or particle diameter, zinc dust with organic surface treatment, zinc alloy pigments and zinc pigments with an addition of nanoparticles. It has been found that many of the formulations have better anticorrosive effectiveness than commercial zinc-rich primers, as well as better impact resistance and flexibility. Such modifications could also leverage the use of these primers on the worse prepared surface, which is extremely important during on site works, and especially during maintenance works.
Keywords: zinc primers, corrosion protection, coating systems, testing
2019, Vol. 62, nr 9, pp. 297-305
New coatings with the addition of pigment based on composite of polyaniline with core and nano-TiO2 to improve their anticorrosive resistance
NanoPure Sp. z o. o., Warszawa
The polyaniline-core-nano-TiO2 composites were prepared by in situ oxidative polymerization of aniline in solutions of two different inorganic acids. The corrosion tests were carried out on carbon steel substrates coated by alkyd coatings (using frame film applicator, one-coat application) containing as the anticorrosion pigments 0.5 mass% of these composites in comparison to coating modified with the same amount of polyaniline composites. The salt spray and EIS (Electrochemical Impedance Spectroscopy) investigations were carried out according to the PN-EN 9227:2012 and PN-EN ISO 16773-2:2008 standards. The EIS test was performed for six weeks, with weekly impedance measurements. The results showed highest anticorrosion resistance of coatings modified with PANI-zinc-oxalate-nano-TiO2 composites, especially the composite obtained in solution of hydrochloric acid.
Keywords: corrosion, steel, anticorrosive tests, anticorrosive pigments, conductive polymers, titanium dioxide
2019, Vol. 62, nr 9, pp. 306-309