Enhancement of Coating Features by Supporting Zinc-Based Coating with Cataphoresis Process: Effect of Acidity and Coating Thickness on the Coating Quality

İngilizce (OpenAlex)

In this work, two hot-forged cast materials that are often used in the automobile sector were employed to produce cast elements with enhanced corrosion performance at low microns by combining two forms of cost-effective coatings (zinc + cataphoresis). In the context of the investigation, firstly 5-8 µm or 12-15 µm zinc-coating in an alkaline (Zn, Zn-Fe, Zn-Ni) or an acidic (Zn, Zn-Ni) environment, followed by 20-25 µm cataphoresis-coating were performed on GGG40 cast-parts. Ink, hogabom, shock, pull-off adhesion, water resistance, salt spray, stone impact, cyclic-corrosion, and scab-corrosion performance tests were implemented for characterization. In addition, the zinc-coating thickness and the phosphate-crystal appearance were evaluated in the x-ray diffraction laminography instrument and the scanning electron microscope. The tensile strengths were determined by the pull-off adhesion test between 171 and 433 psi. The coating thicknesses of zinc-coated parts in alkaline and acidic environments were assigned in the range of 5.88-7.18 µm and 12.10-12.96 µm. Due to the characterization results; it was deduced that the cataphoresis-coating after all zinc-based-coatings under alkaline medium did not afford the required quality and corrosion protection, while cast parts coated under acidic medium before cataphoresis-coating gave appropriate corrosion performance, thus the low-cost coatings could be performed with the eligible properties.