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For at beskytte kemisk sårbare substrater mod korrosive kemikalier anvendes specialmalinger, der danner en svært gennemtrængelig fysisk barriere. Men holder malingerne til metanol?

A new method for testing materials under simulated fire conditions is introduced. The fundamentally new approach relies on the movement of the sample through zones with a spatially increasing temperature. Adjusting the velocity profile with which the sample is moved makes it possible to expose it to practically any temperature-time curve defined in fire safety standards, from extremely rapid hydrocarbon to more gradual cellulosic fire conditions. This manuscript presents a prototype named CoaST-Fire that capitalises on this concept by combining a vertical tube furnace with a vertical motion system. The methodology to calibrate the furnace temperature profile, as well as to calculate the velocity profiles are discussed. The velocity profiles are then used to replicate a range of temperature-time curves with exceptional accuracy and reproducibility. A numerical model is developed in COMSOL Multiphysics to study heat fluxes towards the steel substrate as a function of time and thermal insulation. Finally, proof-of-concept experiments with two commercial intumescent coatings are presented. The experiments are shown to be highly repeatable while images of the coatings during the experiments can provide additional insights into the occurring reaction steps. Furthermore, CoaST-Fire makes it possible to conduct experiments under various O-2 concentrations and could later be extended with a gas outlet analysis system. The study is in line with recent efforts to develop cheaper and more rapid testing methods for early research and development of intumescent coatings and the setup could potentially also be used to test other types of materials.

Silica aerogel-encapsulated biocide crystals can potentially enhance the protection efficiency of antifouling coatings, thereby lowering the impact on nontarget aquatic life. In the present study, copper pyrithione (CuPT) crystals are encapsulated by silica aerogel to obtain loadings of 50-80 wt % CuPT. For optimal design of the heterogeneous particles and mapping of the underlying biocide release mechanisms, the aerogel-encapsulated biocide crystals are characterized by scanning (transmission) electron microscopy, energy-dispersive X-ray spectroscopy, thermal gravimetric analysis, mercury intrusion porosity, Brunauer-Emmett-Teller analysis, and light scattering. The microscopic examination demonstrates that the elongated CuPT crystals are encapsulated by a thin highly porous silica layer. When varying the CuPT loading of the aerogels, it is possible to tune the particle size, pore volume, and specific surface area of the aerogels. Furthermore, this study suggests that the hydrophilic aerogel-encapsulated CuPT, when used in antifouling coatings, attracts seawater and contributes to an efficient controlled release of active CuPT.

Near- and mid-infrared optical coherence tomography (OCT) is evaluated as a non-destructive and non-contact reflection imaging modality for inspection of industrial and marine coatings. Near-infrared OCT was used to obtain high-resolution images (~6/2 µm lateral/axial) of hidden subsurface cracks and defects in a resin base coating, which had been exposed to high pressure and high temperature to study coating degradation in hostile environments. Mid-infrared OCT was employed for high-resolution (~15/8.5 µm lateral/axial) subsurface inspection of highly scattering marine coatings, demonstrating monitoring of wet film thickness and particle dispersion during curing of a 210 µm layer of antifouling coating, and detection of substrate corrosion through 369 µm of high-gloss alkyd enamel. Combining high-resolution and fast, non-invasive scanning, OCT is therefore considered a promising tool for studying coating performance and for industrial inspection.