A high-performance Ti-Zr Based Chromium-Free Conversion Coating on 2024 Aluminum Alloy

摘要

In order to further improve the corrosion resistance of the chromium-free Ti-Zr conversion coating on2024 aluminum alloy (AA2024), a novel Ti-Zr based conversion coating on AA2024 is successfullyprepared by introducing the cathodic inhibitor of benzimidazole into the Ti-Zr conversion solution.After the conversion treatment, AA2024 substrate is well covered with the porous Ti-Zr conversioncoating composed of the micron-sized particles. And the Ti-Zr conversion coating mainly consists ofthe metallic oxide (TiO2, ZrO2, Al2O3), metallic fluoride (ZrF4 and AlF3) and C-N complex. Moreimportant is that there are no apparent corrosion products or detects could be observed during thewhole 168 h NSS test, indicating the significantly excellent corrosion resistance for AA2024 with Ti- Zr conversion coating compared with other chrome-free conversion coatings. The electrochemicalmeasurements indicate the corrosion resistance of the Ti-Zr conversion coating is not so outstanding atthe initial stage, what is worth cherishing is that its anti-corrosion property is gradually improving inthe following period. Therefore, the Ti-Zr conversion coating with excellent corrosion resistance mightbe a promising high-performance protective coating for AA2024 compared with other chrome-freeconversion coating.