As part of an extensive research program to study recent, unexpected intergranular corrosion (IGC) on 6xxx series aluminum alloys (AlMgSi), this paper investigates the mechanism of initiation and early propagation of IGC on the extruded AA6005-T5 alloy with small Cu content (0.1 wt%) by use of advanced electron microscopy techniques applied for near surface characterization. Corrosion testing was restricted to the accelerated IGC test according to the standard BS ISO 11846, involving exposure to acidified chloride solution. The effect of modifying the as-received extruded surface by metallographic polishing, argon sputtering, and alkaline etching was investigated. Initiation of IGC was delayed on the as-received surface compared to the modified surface, caused by the presence of an approximately 8 nm thick crystalline oxide layer formed during extrusion. IGC initiated at the primary α-Al(Fe,Cu,Mn)Si particles for all types of surfaces. However, these particles corroded rapidly in the test solution forming a residue of Cu and Si on the exposed particle surface. This phenomenon, as well as enrichment of Cu on the Al matrix surface by dealloying, contributed increasingly to the formation of new effective cathodic sites and continuing propagation of IGC. The AlMgSiCu (Q) phase, present as primary and secondary particles, was relatively inert against both oxidation and reduction.

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Natural fibrils derived from biomass were used as a template to synthesize uniformly decorated nanoparticles (10–12 nm) of molybdenum carbide (Mo 2 C) and molybdenum nitride (Mo 2 N) supported on carbon. The nanoparticles have been synthesized through the carburization and nitridation of molybdenum on cotton fibrils, using a high-temperature solid-state reaction. The catalyst exhibits an onset potential of 110 mV and an overpotential of 167 mV to derive a cathodic current density of 10 mA cm –2 . The electrocatalyst also demonstrates excellent long-term durability of more than 2500 cycles in acidic media with a Tafel slope value of 62 mV dec –1 .

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