Electrochemical performance of sol–gel derived phospho-silicate-methacrylate hybrid coatings

Recent Progress of Polymeric Corrosion Inhibitor: Structure and Application

An anti-corrosion inhibitor is one of the most useful methods to prevent metal corrosion toward different media. In comparison with small molecular inhibitors, a polymeric inhibitor can integrate more adsorption groups and generate a synergetic effect, which has been widely used in industry and become a hot topic in academic research. Generally, both natural polymer-based inhibitors and synthetic polymeric inhibitors have been developed. Herein, we summarize the recent progress of polymeric inhibitors during the last decade, especially the structure design and application of synthetic polymeric inhibitor and related hybrid/composite.

In Vitro Corrosion Resistance of a Layer-by-Layer Engineered Hybrid Coating on ZK60 Magnesium Alloy

Magnesium alloys are next generation biodegradable implants for clinical applications. However, their medical applications are currently hampered by their rapid corrosion rate in the physiological environment. To overcome such limitations, we have applied a novel layer-by-layer engineering approach of introducing anodization-induced microrough oxidized surface on ZK60 magnesium alloy, followed by surface mineralization with natural calcium apatite (hydroxyapatite, HA), and surface coating with natural protein (silk fibroin, SF); which, effectively reduces corrosion and degradation rate of ZK60 in simulated body fluid. Anodization of ZK60 improved the surface adhesion strength of HA layer; HA layer increased the surface roughness, hydrophilicity and micro-hardness, whereas decreased ionic release; SF layer decreased surface microroughness and hydrophilicity, whereas improved the stability of HA layer. The SF + HA coating on anodized ZK60 effectively decreased the in vitro weight loss (degradation) by almost six times, whereas corrosion rate by more than two orders in magnitude. Such interfacial coatings, with biocompatible SF on the outer surface, could potentially expand the application of ZK60 in the field of biomedical engineering.

Engineering a Bioactive Hybrid Coating for In Vitro Corrosion Control of Magnesium and Its Alloy

Magnesium (Mg) and its alloys are promising biodegradable metallic implant materials. However, their clinical applications are limited by their fast corrosion rate in the biological environment. In this work, with an outlook to improve the in vitro corrosion resistance of Mg and WE43 Mg alloy, a layer-by-layer interfacially engineered anticorrosive and bioactive coating consisting of a natural oxide lower layer, hydroxyapatite (HA) middle layer, and silk fibroin (SF) top layer was fabricated and investigated. Anodization was used to create natural oxide layer induced microroughness on substrates. The electrochemically deposited HA layer improved the surface microroughness and microhardness but significantly decreased Mg ion release, hydrogen gas evolution, and weight loss in simulated body fluid. The spin-coated SF layer further decreased hydrophilicity, in vitro degradation, and corrosion rate. The nonspecific and specific intermolecular interactions between fabricated layers along with their mechanical interlocking interface contributed to improved adhesion strength and integrity of the coating. The SF+HA-coated samples showed enhanced degradation and corrosion resistance due to a synergistic effect of the underlying HA layer, hindering the ingress of aggressive ions and the top hydrophobic SF layer, preventing the ingress of corrosive solution. The SF+HA-coated Mg and WE43 Mg alloy samples exhibited 50 and 26 times decreased corrosion rate, respectively, compared to uncoated samples. Moreover, in vitro cytotoxicity and cell culture studies using a mouse fibroblast cell showed that the SF+HA hybrid coating improved the cell viability, attachment, and proliferation, with cells exhibiting elongated morphology on coated samples as compared to a round shape on uncoated samples.

Microroughness induced biomimetic coating for biodegradation control of magnesium

Herein we explore a combination of anodization induced micro-roughness and biomimetic coating on pure magnesium (Mg) metal at different applied voltages to control adhesion, biodegradation, and corrosion performance in simulated body fluid solution. The anodic film was fabricated using two different potentials, 3 and 5 V, respectively, to create microroughness on the Mg surface. The microroughened Mg surface was subsequently coated with a biomimetic silk thin film; and the characteristics of the treated Mg-substrates were evaluated using various spectroscopic, microscopic, immersion, and electrochemical techniques. A number of independent measurements, including hydrogen evolution, weight loss and electrochemical methods were employed to assess the corrosion characteristics. The silk-coated anodized samples revealed dramatically reduced degradation rate in terms of volume of hydrogen gas generation and weight loss compared to the respective anodized but uncoated, which revealed that optimized biomimetic silk-coated Mg surface (anodized at 5 V and subsequently biomimetic silk-coated ANMg_5V) exhibited the best corrosion performance among all other tested samples. The ANMg_5V Silk showed the highest polarization resistance (46.12 kΩ·cm²), protection efficiency (>0.99) and lowest corrosion rate (only 0.017 mm/year) relative to untreated Mg (8.457 mm/year), and anodized Mg (1.039 for anodized at 3 V and 0.986 for anodized at 5 V) surface due to the formation of a pore-free dense biomimetic protective film over Mg surface. The results of the cytotoxicity test confirm that silk-coated samples are significantly less cytotoxic compared to bare and anodized Mg samples. With enhanced corrosion resistance and cytocompatibility, silk-coated Mg could be a potential material for clinical applications.

Magnesium Alloys With Tunable Interfaces as Bone Implant Materials

Magnesium (Mg) based biodegradable materials are a new generation orthopedic implant materials that are intended to possess same mechanical properties as that of bone. Mg alloys are considered as promising substitutes to permanent implants due to their biodegradability in the physiological environment. However, rapid corrosion rate is one of the major constraints of using Mg alloys in clinical applications in spite of their excellent biocompatibility. Approaches to overcome the limitations include the selection of adequate alloying elements, proper surface treatment, surface modification with coating to control the degradation rate. This review focuses on current advances on surface engineering of Mg based biomaterials for biomedical applications. The review begins with a description of corrosion mechanism of Mg alloy, the requirement for appropriate surface functionalization/coatings, their structure-property-performance relationship, and suitability for biomedical applications. The control of physico-chemical properties such as wettability, surface morphology, surface chemistry, and surface functional groups of the coating tailored by various approaches forms the pivotal part of the review. Chemical surface treatment offers initial protection from corrosion and inorganic coating like hydroxyapatite (HA) improves the biocompatibility of the substrate. Considering the demand of ideal implant materials, multilayer hybrid coatings on Mg alloy in combination with chemical pretreatment or inorganic HA coating, and protein-based polymer coating could be a promising technique to improve corrosion resistance and promote biocompatibility of Mg-based alloys.

Effects of sol–gel process parameters on the anticorrosive performance of phosphosilicate hybrid coatings for carbon steel: structural and electrochemical studies

The effects of several sol–gel process parameters such as acid catalyst addition and the heat treatment procedure on porosity and anticorrosive properties were investigated for phosphosilicate sol–gel hybrid coatings prepared from 3-[(methacryloyloxy)propyl] trimethoxysilane (MEMO) and bis-[2-(methacryloyloxy)ethyl] phosphate (BMEP).

Plasma polymerisation of an allyl organophosphate monomer by atmospheric pressure pulsed-PECVD: insights into the growth mechanisms

This study highlights the growth mechanisms involved in the atmospheric pressure plasma polymerisation of a phosphorus-containing monomer.