The corrosion processes of AA 2024 were analysed via the combined approach of advaced in situ and ex situ analytical tools. Firstly, IR reflection-absorption spectroscopy enabled the identification of a pseudo-boehmite layer on initial surface, which remained present also after the ex situ spectroelectrochemical treatment at different potentials. Secondly, formation of oxyhydroxides was confirmed by confocal Raman spectroscopy. To get a deeper insight into the morphology changes, a three-electrode in situ electrochemical AFM cell was constructed. The results of in situ measurements revealed a gradual increase in the surface roughness. Trenching around intermetallic particles and corrosion deposites were also observed.
COBISS.SI-ID: 5852442
The organic-inorganic protective coatings for the aluminium alloy AA 2024-T3 were produced from a precursor 1,2-bis(trimethoxysilyl)ethane. The structural properties of the coatings were analysed using SEM, EDS, contact angles and IR reflection-absorption at the near grazing incidence angle conditions. Moreover, the forced degradation of the protective coatings at the anodic potentials was studied by various means of the ex situ and in situ analytical approaches with the aim to verify their applicability. The ex situ IR reflection-absorption spectroscopy revealed the prominent changes in the bands like hydration of coatings, cleavage of some siloxane bonds, changes in the regions of C-H vibrations and breaking of some Si-O-Al bonds. The in situ electrochemical AFM approach revealed a decrease in the surface roughness during immersion of the coating, followed by the pretty similar values during application of the chronocoulometric pulses. The impedance spectroscopy indirectly confirmed a gradual dissolution/degradation of the coating.
COBISS.SI-ID: 5825050
The combined effect of hydrophobic poly(dimethylsiloxane) chains and polyhedral oligomeric silsesquioxanes in protective coatings for AA 2024 alloy was investigated using standard electrochemical techniques. The coatings were subjected to ex situ and in situ vibrational spectroscopies to follow the changes in the bands of protective coatings during forced anodic polarisation. The ex situ IR reflection–absorption measurements were performed under near-grazing conditions (80°), yielding changes mainly in the C–H stretching region. Confocal Raman measurements were made under in situ conditions in a specially designed spectroelectrochemical cell. The results that could be obtained with both vibrational techniques are presented.
COBISS.SI-ID: 5491226
The aim of this work was to investigate the protective behaviour of bis-(3-(3-(3-triethoxysilyl)propyl)thioureido)propyl terminated poly(dimethylsiloxane) (PDMSTU) pre-treatment coatings on the AA 2024 aluminium alloy. The silane solution was modified by the addition of bis-([3-(triethoxysilyl)propyl]tetrasulphide) (BTESPT) and trisilanol-heptaisooctyl-POSS in order to introduce better crosslinking and improved mechanical and electrochemical stability in the silane primer coating. The corrosion behaviour of the protected AA 2024 alloy was studied during immersion in 0.5 M NaCl solution, using potentiodynamic polarisation measurements and eventual structural changes were followed using in situ Raman spectroelectrochemical technique. The electrochemical experiments showed that the presence of BTESPT and trisilanol-heptaisooctyl-POSS molecules improves the protective behaviour of the silane coating, while Raman imaging was used to determine their distribution in coatings.
COBISS.SI-ID: 6067226
Fluoropolymer conformal coatings were applied to electronic boards (EBs) and cured at room temperature or 80°C. The coatings were first deposited on model substrate, i.e. aluminium alloy AA 2024 and tested for their anticorrosion properties with a potentiodynamic polarisation technique. The cathodic current densities ranged from 10−9 to 10−10 A/cm2, approaching the lower current limit after the addition of TiO2 nanoparticles into the formulation. Application of fluoropolymer-based formulation was performed via spray-coating deposition. Examination of the coverage of EBs under UV light, which is commonly used in industry, revealed that some components might not be entirely covered. In the search for other possible analytical tools of coverage with protective coatings, optical microscopy and confocal Raman spectroscopy were investigated.
COBISS.SI-ID: 5544986