Effect of Substrates Performance on the Microstructure and Properties of Phosphate Chemical Conversion Coatings on Metal Surfaces

• Published in: Molecules (Basel, Switzerland) Vol. 27; no. 19; p. 6434
• Main Authors: Du, Chunmiao, Zuo, Kangqing, Ma, Zongliang, Zhao, Minru, Li, Yibo, Tian, Shuai, Lu, Yupeng, Xiao, Guiyong
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 29.09.2022; MDPI
• Subjects: Alloys; Analysis; Bacterial infections; Biocompatibility; Biomedical materials; Bonding strength; Chemical reactions; Coatings; Contact angle; Conversion coatings; Corrosion and anti-corrosives; Corrosion mechanisms; Corrosion potential; Corrosion resistance; Crystals; deposition mechanism; Electrochemical corrosion; Electrochemistry; Electrodes; Interface reactions; Intermetallic compounds; Metal surfaces; Metals; Microstructure; Orthopedics; Phase composition; phosphate chemical conversion; Phosphates; Phosphating (coating); Physiology; Scanning electron microscopy; Structure; Substrates; Surface properties; Surface roughness; Thickness; titanium alloy; Titanium alloys; Transplants & implants; Zinc; zinc alloy; Zinc base alloys; Zinc coatings; zinc-phosphate coating; China; Japan; Germany
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules27196434

Phosphate chemical conversion (PCC) technology has attracted extensive attention for its ability to regulate the surface properties of biomedical metals. However, titanium (Ti)-based alloys exhibit inertia because of the native passive layer, whereas zinc (Zn)-based alloys show high activity in acidic PCC solutions. The substrate performance affects the chemical reaction in the phosphating solution, which further leads to diversity in coating properties. In this work, the zinc-phosphate (ZnP) coatings are prepared on Ti alloy (TA) and Zn alloy (ZA) substrates using the PCC method, respectively. The coatings prepared herein are detected by a scanning electron microscope (SEM), X-ray diffractometer (XRD), laser scanning confocal microscope (LSCM), universal testing machine, contact angle goniometer, and electrochemical workstation system. The results show that the substrate performance has little effect on the phase composition but can significantly affect the crystal microstructure, thickness, and bonding strength of the coatings. In addition, the ZnP coatings improve the surface roughness of the substrates and show good hydrophilicity and electrochemical corrosion resistance. The formation mechanism of the ZnP coating is revealed using potential-time curves, indicating that the metal–solution interfacial reaction plays a dominant role in the deposition process.