Rameez Ud Din

Performance Comparison of Steam-Based and Chromate Conversion Coatings on Aluminum Alloy 6060

In this study, oxide layers generated on aluminum alloy 6060 (UNS A96060) using a steam-based process were compared with conventional chromate and chromate-phosphate conversion coatings. Chemical composition and microstructure of the conversion coatings were investigated and their corrosion performance was evaluated using potentiodynamic polarization, acetic acid salt spray, and filiform corrosion testing of powder coated specimens. The steam-based process resulted in homogenous growth of oxide layer and superior coverage over intermetallic particles when compared to chromate-based conversion coatings. The coating formed by steam showed improved corrosion resistance, while adhesion to powder coating and filiform corrosion was comparable with chromate conversion coatings.

Parametric Study of Solder Flux Hygroscopicity: Impact of Weak Organic Acids on Water Layer Formation and Corrosion of Electronics

The presence of solder flux residues on the printed circuit board assembly surface is an important factor contributing to humidity-related reliability issues that affect device lifetime. This investigation focuses on understanding the hygroscopic nature of typical wave solder flux activators—weak organic acids—under varied temperature conditions. In situ x-ray diffraction measurements assessed the effect of high temperature on the crystal structure of organic activators. The hygroscopicity studies were carried out under relative humidity (RH) levels varying from 30% to ∼ 99% and at temperatures 25°C, 40°C, and 60°C. Water absorption levels were determined using the gravimetric method, and the influence on reliability was assessed using electrochemical impedance and leak current measurements performed on the surface insulation resistance comb patterns. The corrosion studies were correlated with the hygroscopicity results and solubility data. Corrosion morphology was analysed using the optical microscopy and scanning electron microscopy. The results show that the hygroscopic nature of typical solder flux residue depends on its chemical structure and temperature. An increase of temperature shifts the critical RH level for water vapour absorption towards lower RH range, accelerating the formation of a conductive electrolyte and the occurrence of ion transport-induced electrochemical migration. The overall ranking of flux activators with the increasing order of aggressivity is: palmitic < suberic  < adipic < succinic < glutaric < dl-malic acid.

False-positive result when a diphenylcarbazide spot test is used on trivalent chromium-passivated zinc surfaces: DPC TEST ON TRI-CHROME-PASSIVATED ZINC

A colorimetric 1,5‐diphenylcarbazide (DPC)‐based spot test can be used to identify hexavalent chromium on various metallic and leather surfaces. DPC testing on trivalent chromium‐passivated zinc surfaces has unexpectedly given positive results in some cases, apparently indicating the presence of hexavalent chromium; however, the presence of hexavalent chromium has never been confirmed with more sensitive and accurate test methods.