Luminescent micro-photo-images (MPI) for digitalization of diffusant penetration into epoxy binders and adaptive composites for anticorrosive coatings

• V.A. Shchelkov and A.B. Il’in

Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31-4, Leninsky prospect, 119071 Moscow, Russia

Abstract: Diffusion studies of the penetration of phosphoric acid, dimethyl sulfoxide, and methyl ethyl ketone solutions into modified amine-cured epoxies were conducted. For an exposure time of 11.568 hours at +50°C, the penetration depth of 60% of the phosphoric acid was determined using local X-ray spectral analysis, micro-luminescence spectroscopy, and the luminescent drop indicator method. The outer zone of polymer fluorescence change causes internal stresses arising from phosphoric acid swelling in the region ahead of the acid penetration front boundary of 1237 μm and with a radius of approximately 20 μm. Differences in the appearance of a visible state in the “green”, “blue”, and “red” color sectors were revealed due to the fluorescence diffusion zone and the region of the original polymer preceding it. Transmission distribution histograms were constructed for modifying composite microcapsules containing an inhibitor block, enabling digitalization of the process flow and calibration sieving modes for the microencapsulated inhibitor code. Focused images with highly developed reflection relief were constructed for multiple time exposures, resulting in a series of high-resolution microphotographs (4096×3288 pixels). It has been shown that under various spectral conditions of fluorescence observation (UV (ultraviolet) 250–290 nm/330–400 nm, V (violet-blue) 395–415 nm/420–500 nm, B (blue) 420–485 nm/480–700 nm and G (green) 460–550 nm/600–700 nm) of epoxy binders and soft composites exposed in phosphoric acid or dimethyl sulfoxide, it is possible to digitalize photomicrographs (PMI) (Altami LUM-1-LED microscope; Altami UCMOS-14000-KPA video camera; Altami Studio software) for multifractal analysis.

Keywords: epoxy binder, adaptive composite, anti-corrosion coating, internal stresses, phosphoric acid, dimethyl sulfoxide, fluorescence spectrum, phosphorescence time, micro-photo-images, digitalization, multifractal analysis

Int. J. Corros. Scale Inhib., 2025, 14, no. 4, 2379-2396
doi: 10.17675/2305-6894-2025-14-4-35

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