Nano-TiO2 Phosphate Conversion Coatings – A Chemical Approach

Abstract

The present study aims at deposition of zinc phosphate coatings on low carbon steel with incorporated nano-TiO 2 particles by chemical phosphating method. The coated low carbon steel samples were assessed in corrosion studies using electrochemical impedance spectroscopy and potentiodynamic polarization techniques (Tafel) in 3.5% NaCl solution. Morphology and chemical composition of the coatings were analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy in order to observe growth of coating. Significant variations in the coating weight, porosity and corrosion resistance were observed with the addition of nanoTiO 2 in the phosphating bath. Corrosion rate of nano-TiO 2 chemical phosphate coated samples was found to be 3.5 milli inches per year which was 3 times less than the normal phosphate-coated sample (8 mpy). Electrochemical impedance spectroscopy studies reveal reduction of porosity of nano-TiO 2 phosphate coated samples. It was found that nano-TiO 2 particles in the phosphating solution yielded uniform phosphate coatings of higher coating weight, fewer defects and enhanced corrosion resistance than the normal zinc phosphate coatings (developed using normal phosphating bath).

Synergistic Effects of 1-Octyl-3-Methylimidazolium Hexafluorophosphate and Cellulose Nanocrystals on Improving Polyacrylate Waterborne Anti-Corrosion Coatings

“…The shrinking semicircles during the immersion test exhibit the declining anti-corrosion performance. The initial linear portion of the curve shown in Figure 2 c could be attributed to the pseudo-two-time constant phenomenon caused by the penetration of electrolytes through the coating defects [ 21 , 22 ]. Moreover, an electrical equivalent circuit was applied to model Nyquist plots for quantitative evaluation.…”

“…One explanation for this is the enhancement of the barrier effect after introducing CNCs into the coating [ 10 ]. Another possible reason may be a pseudo-two-time constant phenomenon after the penetration of electrolytes [ 21 , 22 ], which interferes with the curve fitting, resulting in a larger R C value than the real value. During the immersion process, the R C of the C 8 mimPF 6 -CNCs sample had the highest values of 18,670 and 7865 Ω cm 2 at the initial stage and after 96 h of immersion, respectively.…”

Preparation of Zn5Mo2O11·5H2O@Sulfonated Graphene by Template Method and Its Anticorrosion Mechanism in Polyurethane Coatings

“…In the equation, P is porosity, R ps is the polarization resistance of the substrate, R p is the polarization resistance of the samples, ∆E corr is the potential difference between the uncoated and the coated substrate, b a is the anodic Tafel coefficient of the substrate. The electrochemical parameter of carbon steel can be obtained from the related reference [64,65]. In Table 3, the 3 wt% SZMO@SG coatings have the lowest porosity.…”

Melatonin as an Accelerating Agent for Phosphate Chemical Conversion Coatings on Mild Steel with Enhanced Corrosion Resistance

“…34 Other works have also reported the effects of nanoparticles on phosphate coatings. [35][36][37] Results show that nanoparticles have a certain refinement effect on phosphate crystals, and improve the corrosion resistance of phosphate coatings. 38,39 However, it is well known that nanoparticles are easy to agglomerate, which would seriously impact the stability of a phosphating bath.…”