20.500.12556/DiRROS-31130 Corrosion resistance of different commercial Zr, Zr/Ti and Zr/Cr(III) conversion coatings deposited on an Al alloy 3003 Chromate-free conversion coatings are increasingly investigated as environmentally acceptable alternatives to conventional chromate conversion coatings for corrosion protection of aluminum alloys. In the present study, the electrochemical behaviour and long-term corrosion stability of several commercial conversion coating systems based on trivalent chromium (TCP), zirconium (ZrCC) and zirconium/titanium (Zr/TiCC) were systematically evaluated on AA3003 aluminum alloy and compared to chromate conversion coating (CCC) CR614. Three TCP coatings (ST650, MC1300 and B30002), two ZrCC (MC1700 and MC160/161), and one Zr/TiCC (B2040) were investigated. Coatings were prepared at pre-selected pH and concentration, but at varying conversion times. The protective performance of the coating was then tested across various exposure conditions using potentiodynamic polarization measurements: (i) after 24 h of exposure to air, (ii) after 24 h of immersion in 3.5 wt.% NaCl solution and (iii) simulated acid rain solution, and (iv) after exposure in a salt spray chamber for 500 h. The protective performance strongly depended on both the conversion conditions and the exposure environment. The optimal conversion times ranged between 40 s and 18 min, depending on the coating type. Differences between the investigated systems remained relatively limited when investigated after exposure to air and immersion in the simulated acid rain solution. However, in chloride-containing environments, substantially greater differentiation between the coatings was observed. Among the investigated systems, TCP coatings exhibited the most favourable overall corrosion performance, particularly after prolonged salt spray exposure, where ST650 and B30002 polarization resistance values were approximately 8800 and 5300 kΩ cm2, respectively, together with corrosion current densities as low as 0.0004 and 0.001 μA cm−2. ZrCC systems MC1700 and MC160/161 also provided significant corrosion protection, achieving polarization resistance values around 2700 and 2400 kΩ cm2 after 500 h of salt spray exposure, whereas the Zr/TiCC coating B2040 exhibited poorer long-term performance. The results further demonstrated that prolonged salt spray exposure provides considerably more realistic evaluation of long-term coating protectiveness than short-term electrochemical measurements alone. Overall, optimized TCP and ZrCC systems provided corrosion protection under chloride-containing conditions comparable to or superior to the investigated conventional chromate conversion coating CR614 deposited on AA3003 alloy. chromate-free conversion coatings premazi brez kromatov true false true MDPI Švica Angleški jezik Slovenski jezik © 2026 by the authors. Neznano 2026-07-14 10:20:18 2026-07-14 10:20:18 2026-07-15 03:49:17 0000-00-00 00:00:00 2023 0 0 Nasl. z nasl. zaslona; Opis vira z dne 14. 7. 2026; str. 1-29 iss. 7, [article no.] 730 Vol. 16 Jul. 2026 0000-00-00 Zaloznikova Objavljeno apc 2026-06-03 2026-06-28 2026-07-02 54 2075-4701 284668931 https://www.mdpi.com/2075-4701/16/7/730 1 da34e227-7f5c-11f1-b063-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=47997 RAZ_Mujdrica_Kim_Maja_2023.pdf RAZ_Mujdrica_Kim_Maja_2023.pdf 1 0B33F134C65C8A4BF9ECB905F487890B d98e1bf0f521886f0cb8d7cd7312dc718a1bdcbcf22654ec752584040d1c855a 1c7bebb0-7f5d-11f1-b063-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=47998 Institut Jožef Stefan 0 0 0