The Effect of Residual Solvent in Carbon-Based Filler Reinforced Polymer Coating on the Curing Properties, Mechanical and Corrosive Behaviour.

Solution mixing, which is one of the standard methods of producing Graphene-based Nanocomposites (GPC) may not be as efficient as it is expected due to the presence of residual solvent in the cured product. Therefore, the influence of including acetone in the preparation of Graphene Oxide-based epoxy coating (GO-EP) on the curing behaviour, mechanical and corrosive behaviour was studied. FTIR and TGA analysis confirmed that the GO-EP prepared by ultrasonication (GO-EP U) indicated the presence of more low-molecular-weight/low crosslinked (LMW/LC) sites than GO-EP prepared by stirring (GO-EP MS). Meanwhile, the tensile strength and hardness of GO-EP MS was 20% and 10% better than GO-EP U which confirmed that the presence of a lower number of LMW/LC could prevail over the agglomeration of GO sheets in the GO-EP MS. Pull-off adhesion tests also confirms that the presence of remaining acetone would cause the poor bonding between metal and coating in GO-EP U. This is reflected on the electrochemical impedance spectroscopy (EIS) results, where the GO-EP U failed to provide substantial barrier protection for carbon steel after 140 days of immersion in 3.5 wt% NaCl. Therefore, it is essential to consider the solvent effect when solvent is used in the preparation of a coating to prevent the premature failure of high-performance polymer coatings.

Mechanical Performance and Corrosion Behaviour of Diffusion-Bonded A5083 Aluminium and A36 Mild Steel with Gallium Interlayer.

This article investigated the mechanical performance and corrosion behaviour of a diffusion-bonded A5083 aluminium/A36 mild steel dissimilar joint with a Gallium (Ga) interlayer. The bonding parameters were the bonding temperature (525 and 550 °C), holding time (60 and 120 min) and surface roughness (800 and 1200 grit). Property characterisation was achieved using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, Vickers microhardness tester, Izod impact tester and potentiodynamic polarisation testing. The results revealed that the significance of the bonding parameters was in the order bonding temperature > surface roughness > holding time. Increasing the bonding temperature resulted in an increase in the impact strength and a corresponding reduction in the corrosion rate and microhardness. However, increasing the grit size decreased the microhardness and a corresponding increase in the impact strength and corrosion rate. The impact strength and corrosion rate decreased with the increasing holding time while the microhardness followed a reverse trend. It was also discovered that incorporating the Ga interlayer resulted in a 67.9% improvement in the degradation rate.