Assessment of Paint Layers Quality 1. Field investigations on a railway bridge

Abstract

By electrical determinations, digital microscopy and visual observations, the anticorrosive insulation capacity of the paint layers applied to the three sections of a bridge over the Tisza River was assessed. The visual observations have highlighted the fact that on the Eastern section repainted in 2013, biofouling increases are significant (covers up to 10 % of the surface) - both ferns have been identified (Hypogymnia physodes and Xanthoria parietina), filamentous molds (Aspergillus fumigatus and Aspergillus niger) as well as algae and moss (green - capable of photosynthesis). On paint applied in 1986, no bio fouling was visible but the painting material is aged and shows rust traces (5-10 % of the surface) and exfoliation between the paint layers (10-20 % of the surface). No bio fouling and/ or exfoliation/ degradation of the paint layer have been observed on the paint applied in 2014. Determinations of electrical insulation resistance correlated with those of the paint layers� thickness are closely related to the visual observations. The values obtained for the specific resistivity of the paint layers applied in 2013 (with bio fouling increases) are approx. 38 times lower than those applied in 2014. These findings suggest that the painting material used in 1983 for the top coat realization, showed major qualitative vices.

Assessment of Paint Layers Quality 3. Analysis by SEM-EDAX and XRF techniques of the paint layers applied on a railway bridge

“…This explanation is also supported by the relatively high content of silicon, which suggests that the inorganic filler material (probably barium sulphate) used to achieve the paint applied to the Eastern section was from a mineral source with appreciable impurities of chlorides, phosphates and silicates. The appreciable content of chlorine, phosphorus and potassium (which give lightly soluble salts) of the paint used on the Eastern section can explain both the massive biofouling increases and the substantially lower resistivity of the coating layer on this section (reported in [23]).…”

“…Probably these elements have ensured the mineral salts need for growth and multiplication of the identified and reported microorganisms in [23,24].…”

“…From the three sectors of the bridge presented in [23] repainted in 2014 (the Western sector), samples of painting material were taken. Samples were analysed by SEM-EDAX and XRF techniques.…”

“…Depending on the operating environment during exploitation, the metal structures and the anti-corrosion protection systems with which they are provided are exposed to a number of stress factors such as: mechanical (vibration, trepidation, etc. ), thermal [1,2] climatic [3][4][5][6], non-ionizing radiation in IR and / or UV spectrum [2,4,6,7], chemical [8][9][10][11][12], microbiological [14][15][16][17][18][19][20][21][22][23][24][25] etc.…”

“…Large differences in the behaviour and durability of painting materials applied on different sections of a railway bridge (i.e. exposed to identical climatic conditions) have recently been reported [23], and only on one of the recently repainted sections excessive growths of biofouling were found, including molds, algae, moss and lichens [24]. In view of these considerations, the paper aim is to analyse, by the SEM-EDAX and XRF techniques of the paint samples taken from of the third section of bridge presented in [23] to identify the premature biodegradation causes of paint applied in 2013 and to identify the top coat constituents that favoured the growth of biofouling.…”