2nd Intl Symp. on Corrosion for Sustainable Development

Aluminum alloys find widespread use in industries such as aerospace, automotive, marine, and oil and gas, owing to their exceptional properties. However, their susceptibility to localized corrosion can lead to catastrophic failures in-service. Mechanical surface treatment emerges as a promising approach to enhance the mechanical and corrosion properties of aluminum alloys. Numerous recent studies have investigated the impact of mechanical surface treatment on the corrosion behavior of aluminum in various forms, including cast, wrought, powder metallurgy, and additive manufacturing. This review focuses on the corrosion response of aluminum alloys subjected to different mechanical surface processing techniques. A wide range of processes, such as peening, rolling, extrusion, laser shock peening, and equal channel angular pressing (ECAP), are systematically reviewed. These methods have the potential to significantly alter the microstructure, mechanical properties, and electrochemical response of the aluminum surface. The outcomes of such surface treatments include but are not limited to introduction of a residual stress field, increased dislocation density, grain refinement, enhanced surface roughness, and formation of surface damage or discontinuities. This review discusses the general corrosion behavior, susceptibility to localized corrosion, stress corrosion cracking (SCC), corrosion fatigue, intergranular corrosion, and cavitation, along with the influence of processing parameters on microstructure and corrosion properties. Additionally, a comprehensive comparison of corrosion testing results is provided where applicable.

The design and fabrication of stimuli-responsive smart anti-corrosive coatings with merits of eco-friendliness, multifunctionality and long-acting is a major demand in corrosion protective field, which can be fulfilled by adding smart microcapsules (MCs) into coatings [1,2] Nevertheless, owning to the unclear release controlling mechanism of MCs, the design of high-performance MCs on-demand fails to be achieved. In addition, the existing MCs are mostly fabricated by synthetic materials with undesirable eco-friendliness. On the other hands, although the addition of MCs can significantly improve the corrosion protective performance, this single function fails to fulfill multifunctional integration needs of protective coatings [3,4]. To tackle above issues, a MC is assembled by choosing 2-mercaptobenzimidazole (2-MBI) as inhibitor, HNTs as inhibitor carrier, and ε-PLL, SA as well as CTS as encapsulating polyelectrolytes. The release controlling mechanism was analyzed by UV-vis technique and the key factors regulating inhibitor release rate are also confirmed. In 3.5 wt.% NaCl solutions the inhibitor can be timely released in response to the invasion of water. In addition, the releasing speed was enhanced with the increments of pH values of release mediums. Furthermore, the whole release process can lasts for 216 hours. The release behavior fulfills the requirements of sensitivity, selectivity and sustainability raised by long-term smart anticorrosive coatings. Both the solubility of inhibitor and the porosity of SA layer regulate the release rate of inhibitor. The outermost CTS layer offers MCs superior antimicrobic performance, while the complex encapsulation with ε-PLL and SA significantly prolongs the release process. As comparing with the reference coating, the proposed water-based epoxy coating with 1 wt.% MCs embedded can provide an excellent corrosion protective. In addition, the tensile strength of proposed coating is increased by 20% and the wet adhesion (72 hours) is also increased by 20%. arine environment.

Graphene has triggered unprecedented research excitement for its exceptional characteristics. The most relevant properties of graphene as corrosion resistance barrier are its remarkable chemical inertness and impermeability and toughness, i.e., the requirements of an ideal surface barrier coating for corrosion resistance, thus, an interest in graphene coating as a disruptive approach to corrosion mitigation. However, the extent of corrosion resistance due to chemical vapour deposition (CVD) graphene coatings has been found to vary considerably in different studies. The author’s group demonstrated the ultra-thin graphene coatings developed on copper and nickel by CVD to improve corrosion resistance of the metals by two orders of magnitude in aggressive aqueous chloride environments. In contrast, other reports suggest the graphene coating to actually enhance corrosion rate of copper, particularly during extended exposures. Author’s group has investigated the reasons for such contrast in corrosion resistance due to graphene coating as reported by different researchers, and on the basis of the findings, they have succeeded in developing multilayer graphene coatings that conferred durable corrosion resistance to copper and nickel in the aggressive chloride environment.
Corrosion and its mitigation costs dearly (any developed economy loses 3-4% of GDP due to corrosion, which translates to ~$250b to annual loss USA). In spite of traditional approaches of corrosion mitigation (e.g., use of corrosion resistance alloys such as stainless steels and polymeric coatings), loss of infrastructure due to corrosion continues to be a vexing problem. Therefore, it is technologically as well as commercially attractive to explore graphene coating as a disruptive approach to durable corrosion mitigation. However, developing graphene coating on the most common engineering alloy, mild steel by CVD is a non-trivial challenge. The presentation will discuss the challenges, and their successful circumvention that enabled graphene coatings on mild steel, and presents results demonstrating durable and remarkable corrosion resistance of graphene-coated mild steel.

Great advances have been made in recent years in developing viable theories for stress corrosion cracking (SCC) and corrosion fatigue (CF), particularly with the advent of the Coupled Environment Fracture Model (CEFM) and the Coupled Environment Corrosion Fatigue Model (CECFM), respectfully. Both models are highly deterministic in that the model predictions are constrained by the natural laws, specially by the conservation of charge and mass, Faraday’s law of the equivalence of mass/charge, and by the traditional laws of chemistry. The outcome is that the models can predict the crack growth rate (CGR) under constant loading and under fatigue conditions as accurately as can be measured. The illustration of the application of the models to predicted SCC and CF damage in water-cooled nuclear power rector coolant systems is presented.

The theories for localized corrosion, such s pitting corrosion, stress corrosion cracking, corrosion fatigue, flow-assisted corrosion, and galvanic corrosion, among other mechanisms and general corrosion have tended to develop independently, many on an ad hoc basis. In this paper a unified theory is resented in which all known forms of localized and general corrosion are accommodated under s singly mathematical framework. The physicoelectrochemical factors that lead to the development of one form of attack over anther are identified and are illustrated by reference to specific examples. Knowing these factors allows us to predict the form of attacks (2) that might be expected for any given metal/alloy under any given set of environmental conditions.

Fly ash (FA) is a fine powder collected as residue in the exhaust gases from combustion chambers of pulverized coal fired boilers at thermal power plant stations. It is usually solid, irregularly spherical in shape; at times, it is a cenosphere with a hollow spherical shape. The size, chemical composition and the colour of fly ash vary depending on the coal type used in coal power stations.

Generally, fly ash particles are light to dark-grey in colour with sizes range up to several hundred microns. Fly ash normally consists of predominantly aluminium silicates with a range of other metal oxide being present. It has been used in several areas, such as cement and concrete applications, bricks, highway pavement, road bases, and backfills. In most countries, fly ash is usually under-utilized.

In this study, as received fly ash from Cement Australia owned coal-power furnaces and subsequently modified into near whitened fly ash (with 96 % whiteness of calcium carbonate) – a UNSW developed technology - were utilized as reinforcement in virgin white polymer polyethylene, using up to 50 weight wt. % of fly ash.

Results indicate that near whitened fly ash produces filled polypropylene composites visibly almost as white as the neat PP polymer. Also, tensile modulus and notched Charpy impact properties of the fly ash filled composites are substantially enhanced by the fly ash addition.

Scanning electron microscopy of notched impact fracture surfaces show smaller size fly ash particles are embedded in the interlamellar textural matrix of the polymer, thereby absorbing / transferring significant mechanical energy under impact.