The first steel with improved resistance towards atmospheric corrosion, the so-called weathering steel, was patented in the USA in 1933 and was initially used for coal railway cars, and after that, in building and bridge engineering. Weathering steels show higher corrosion resistance than carbon steels in many types of atmosphere due to their ability to form a compact, stable, adherent and protective patina during the time of exposure. Morphological evaluation of the appearance of the corrosion product layer, together with phase analysis of its components, can enable determination of the type of patina and the degree of protection of the steel. To support the visual assessment of a patina, a check based on the qualitative and quantitative phase analysis of its components may be carried out, and the PAI (Protective Ability Index) can be calculated. The estimation of the corrosion processes on original Polish-made weathering steel (12HNNbA) was carried out on a 30-year-old bridge in Poland. There are some structural problems within the deck derived not only from corrosion but also steel cracking, both inside and outside the boxes, at different heights. Fourteen representative samples of patina were analysed and their phase structures were determined by the X-ray powder diffraction method. The PAIs were determined and analysed.

This study presents an eco-friendly approach to antibacterial polyester powder coatings by incorporating hybrid additives composed of biopolymers immobilized on halloysite nanotubes. Polylysine (PLY) and quaternized chitosan (CH-Q) were used as natural antimicrobial agents, while halloysite (HAL) acted as a carrier to improve dispersion and reduce leaching. HAL/PLY and HAL/CH-Q hybrids were incorporated into polyester coatings and evaluated for morphology, mechanical properties, water resistance, and antibacterial performance (ISO 22196). The HAL/PLY coating demonstrated a strong bactericidal effect, reducing Escherichia coli and Staphylococcus aureus by 99.9989% and 99.9993%, respectively. HAL/CH-Q showed moderate activity against E. coli (50.2323%) but high activity against S. aureus (98.6500%). Immobilization of biopolymers on the halloysite surface improved dispersion and barrier properties while enabling a silver-free antibacterial effect. The results demonstrate a sustainable strategy for multifunctional powder coatings based on naturally derived antimicrobial components.

The effect of pigments and additives on the resistance of organic binders to cyclic changes in temperature, humidity, and UV radiation intensity was investigated. The study involved paints based on two binders used in polyurethane paints, pigmented in various shades of yellow, red, and blue. Both the binders and pigments differed in their weather resistance. The color stability, gloss, water contact angle, and surface energy of the coatings were assessed. Changes in color and gloss depended primarily on UV radiation, while decorative properties depended on the type of pigments in each color group. Smaller changes in color and gloss were caused by changes in humidity and temperature, without the contribution of UV radiation. The more weather-resistant pigmentation protected the binder from degradation, as confirmed by FT-IR.

The durability of coatings is often evaluated by the impact of standardized weathering cycles. While such tests may yield well-differentiated damage patterns, they do not reveal which specific weathering parameters—particularly temperature, moisture, or radiation exposure—contributed to the formation of each observed damage type or to what extent. Consequently, it remains unclear (i) how exactly each individual formulation should be modified in order to optimize coating durability, and (ii) which of the tested coatings are particularly (or less) suitable for specific climatic conditions. In the present study, a testing concept is introduced that is primarily based on conducting single-parameter variants of the fluorescent weathering cycle according to DIN EN ISO 16474-3:A (P1). These variants were designed in such a way that, by comparing the weathering results obtained from sets of three color-identical topcoat systems, conclusions could be drawn regarding the aforementioned aspects (i) and (ii). Indeed, it was demonstrated that formulation modifications derived from the observed results led to a markedly improved weathering stability of the topcoat systems, particularly with respect to their previously identified weaknesses.

On the basis of field studies, the protective properties of various coating systems on bridges in Poland after extended periods of operation according to PN-EN ISO 12944-1:2017 (approximately 15 years) are presented. The evaluation was carried out on the basis of visual damage assessment, tests of coating thickness and adhesion, while selected structures were tested for protective properties evaluated by impedance spectroscopy. The types of damage on the tested structures were compared. The results of the study can be used as a basis for discussion regarding the selection of optimum corrosion protection solutions for bridge structures