Electrochemical Evaluation of Mg and a Mg-Al 5%Zn Metal Rich Primers for Protection of Al-Zn-Mg-Cu Alloy in NaCl

High purity magnesium and a Mg-Al 5wt% Zn metal rich primer (MRP) were compared for their ability to suppress intergranular corrosion (IGC) and intergranular stress corrosion cracking (IG-SCC) in peak aged AA 7075-T651 by sacrificial anode-based cathodic prevention. Tests were conducted in 0.6 M NaCl solution under full immersion. These evaluations considered the ability of the primer to attain an intermediate negative open circuit potential (OCP) such that the galvanic couple potential with bare aluminum alloy (AA) 7075-T651 resided below a range of potentials where IGC is prevalent. The ability of the primer to achieve an OCP negative enough that the AA 7075-T651 could be protected by sacrificial anode-based cathodic prevention and the ability to sustain this function over time were evaluated as a first step by utilizing a NaCl solution. The primers consisted of epoxy resins embedded with either (1) Mg flake pigments (MgRP) or (2) Mg flake pigments and spherical Al-5 wt.% Zn together as a composite (MgAlRP). MgRP was an effective coating for cathodic protection but dispensed less anodic charge than the composite MgAlRP. Cross-sectional analysis demonstrated that some Mg flakes dissolved while uniform surface oxidation occurred on the remaining Mg flakes which led to impaired activation. The composite MgAlRP maintained a suitably negative OCP over time, remained activated, dispensed high anodic charge, and remained an anode in zero resistance ammeter testing. Chemical stability modeling and zero resistance ammeter testing suggest that Mg corrosion elevates the pH which dissolved aluminum oxides and hydroxide thereby activates the Al-5wt.% Zn pigments, thereby providing a primary (i.e. Mg corrosion) and secondary process to enable superior (activation of Al-5wt%Zn) sacrificial anode-based cathodic protection.Comment: 30 pages, 3 tables, 27 figure

Empirical investigation to explore potential gains from the amalgamation of Phase Changing Materials (PCMs) and wood shavings

The reduction of gained heat, heat peak shifting and the mitigation of air temperature fluctuations are some desirable properties that are sought after in any thermal insulation system. It cannot be overstated that these factors, in addition to others, govern the performance of such systems thus their effect on indoor ambient conditions. The effect of such systems extends also to Heating, Ventilation and Air-conditioning (HVAC) systems that are set up to operate optimally in certain conditions. Where literature shows that PCMs and natural materials such as wood-shavings can provide efficient passive insulation for buildings, it is evident that such approaches utilise methods that are of a degree of intricacy which requires specialist knowledge and complex techniques, such as micro-encapsulation for instance. With technical and economic aspects in mind, an amalgam of PCM and wood-shavings has been created for the purpose of being utilised as a feasible thermal insulation. The amalgamation was performed in the simplest of methods, through submerging the wood shavings in PCM. An experimental procedure was devised to test the thermal performance of the amalgam and compare this to the performance of the same un-amalgamated materials. Comparative analysis revealed that no significant thermal gains would be expected from such amalgamation. However, significant reduction in the total weight of the insulation system would be achieved that, in this case, shown to be up to 20.94%. Thus, further reducing possible strains on structural elements due to the application of insulation on buildings. This can be especially beneficial in vernacular architectural approaches where considerably large amounts and thicknesses of insulations are used. In addition, cost reduction could be attained as wood shavings are significantly cheaper compared to the cost of PCMs