Nanocomposite Coatings in Corrosion Protection Applications: An Overview

Corrosion is one of the biggest problems which affects the economy of the country, which occurs as a result of the interaction of the metal with its surroundings. One of the easiest ways to prevent corrosion is coatings of the metals with paint, plastic or wood. Several types of coatings have been adopted by corrosion scientists in the prevention of corrosion that are mainly based on electrochemical principles. Fortunately, based on cost and effectiveness, four types of coatings are variably employed by the metal and metallurgy industries. One among the cheapest and effective way to prevent corrosion is to use barrier coatings like plastic, powder and paint. Hence, nanocomposite coatings by electrochemical deposition offers an excellent, scratch and corrosion resistance on the metal surface. These coatings may be used to restoration of the components instead of interchanging them, resulting in reduced maintenance costs and disturbance. Significant improvements in the corrosion protection of steel have been reported by using metal-metal matrix, metal-metal oxide matrix, metal-polymer matrix, and ceramic-metal matrix nanocomposite. This review presents an overview of works related to nanocomposite coatings and to re-evaluate the literature for the future research in the field that still lacks validation.

Corrosion Behavior of Extruded AM60-AlN Metal Matrix Nanocomposite and AM60 Alloy Exposed to Simulated Acid Rain Environment

The present work compared the initial stages of corrosion process development on the AM60-AlN metal matrix nanocomposite surface and on AM60, during their exposure for 30 days to simulated acid rain solution (SAR). The AlN nanoparticles were observed as “attached” to those of Mn-rich AlMn intermetallic particles, forming clusters. The introduction of 1.0 wt.% AlN (≈ 80 nm) in the AM60 alloy carried a slight grain refinement and favored the formation of a denser and more protective corrosion layer, suggested by the electrochemical impedance spectroscopy (EIS) values of higher charge transfer resistance (R2) and capacitance, characteristic of the double layer in the presence of corrosion products, and also suggested by Rn (EN) values, compared to those of the AM60 alloy. Thus, the concentration of the released Mg-ions from the composite surface was lower. Due to the increase in time of the SAR solution pH, Al de-alloying may occur, as well as Al(OH)3 formation, as confirmed by XPS analysis. Due to the presence of Cl-ions in SAR solution, localized corrosion was observed, suggested as fractional Gaussian noise of a stationary and persistent process in time, according to the PSD of the corrosion current fluctuations (EN).

Regulating Mechanical Properties of Al/SiC by Utilizing Different Ball Milling Speeds

Advanced materials with high strength are in great demand for structural applications, such as in aerospace. It has been proved that fabrication strategy plays a vital role in producing composites to satisfy these needs. This study explores new strategies for flake powder metallurgy, with the aim of designing an effective strategy to achieve the highest possible mechanical strength for a metal matrix nanocomposite without changing the reinforcement fraction. Different strategies were used to regulate the mechanical properties for similar composites based on shift speed ball milling. Ultra-ductile composites on one hand, and ultra-strong composites on the other hand, were fabricated using similar composites. The results demonstrate that shifting the ball milling speed can be used to manipulate the mechanical properties of the composite to achieve the desired properties for any specific application.