Self-Healing Effect by Zinc Phosphate and Calcium Silicate Included in Organic-Inorganic Composite Coating on 55%Al-Zn Coated Steel Sheet

Abstract

Improved corrosion resistance of steel sheets plated with zinciferous metal, and particularly 55% Al-Zn alloy coated steel sheets, has become necessary in recent years. However, 55% Al-Zn alloy coated steel sheets are susceptible to surface cracks during forming due to the hardness of the metallic coating. This research examined various non-chromate corrosion-preventive compounds for organic-inorganic composite coatings and found that a composite coating containing a mixture of Zn 3 (PO 4 ) 2 and CaSiO 3 provided the highest corrosion resistance among all the additives tested. The corrosion mechanism was investigated by post-test analysis of the specimens by SEM, AFM, TEM and EDX, revealing that an amorphous surface layer, which was approximately 30 nm thick and contained Ca, Cr, P, Si, C, and O, had newly formed on the steel surface exposed after deformation of the coating. It is presumed that Ca 2þ and HPO 4 2À were formed by dissolution of the CaO component in CaSiO 3 and hydrolysis of ZnO 3 (PO 4 ) 2 , respectively, and reacted to form an insoluble Ca-phosphoric acid compound which inhibited corrosion of the metal exposed by cracks.

Preparation of microcapsules containing multi-functional reactive isocyanate-terminated-polyurethane-prepolymer as healing agent, part II: corrosion performance and mechanical properties of a self healing coating

“…Therefore, an increase in defects within the coating lm caused a decrease in the overall mechanical properties, as also reported in the literature. [29][30][31] Self-healing coatings with high healing performance are always desirable, while maintaining the mechanical properties. 33 To achieve this goal, a balance between microcapsule loading and mechanical properties should be established.…”

“…In microcapsule-based self healing systems, most research is into the effect of microcapsules on mechanical properties. [29][30][31] Based on previous work, there are different methods to achieve healing efficiency. One of the most common methods is to use a fracture toughness test.…”

General Method for the Synthesis of Ultrastable Core/Shell Quantum Dots by Aluminum Doping

“…Self-passivation was observed in several metals hundreds of years ago. When exposed to air, many metals, including aluminum, chromium, zinc, titanium, and silicon (metalloid), naturally form a hard, relatively inert surface, that can notably slow corrosion of the metal in ambient air. This phenomenon has been widely used in metallurgy to make stainless steel and other alloy metals to avoid corrosion and oxidation.…”

Corrosion behavior of aluminum-Fiber Glass composite fabricated through surface mechanical alloying in alkaline media

“…Explained due to current outflow limited through barrier layers those formed because of micro cavity. Two capacitive loops appeared in 'figure 4(b)' one at high frequency due to redox reactions Al↔Al + being assumed rate determining of charge transfer process [39]. The other appeared at low-frequency attributed due to further redox reaction Al + ↔Al 3+ .…”