Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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The Corrosion Behavior of Anti-Graffiti Polyurethane Powder Coatings

  • Rossi, S. (Department of Industrial Engineering, University of Trento) ;
  • Fedel, M. (Department of Industrial Engineering, University of Trento) ;
  • Deflorian, F. (Department of Industrial Engineering, University of Trento) ;
  • Feriotti, A. (Department of Industrial Engineering, University of Trento)
  • Received : 2018.08.21
  • Accepted : 2018.10.13
  • Published : 2018.12.31
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Abstract

Anti-graffiti coatings have become more important. These layers must guarantee excellent corrosion protection properties, and graffiti must be easily removable, without reducing protection and aesthetic properties. In this study, anti-graffiti and corrosion behavior of two anti-graffiti polyurethane powder coatings were studied. These layers were deposited on aluminum substrate, with two different surface finishes, smooth, and wrinkled. The action of four different removers are investigated. Graffiti were drawn on coatings by means of red acrylic spray paint. Methyl-ethyl-ketone (MEK) and a "commercial" remover were the most effective solvents, in terms of graffiti removal capability, producing limited change in aesthetical surface aspect for smooth finishing. The wrinkled surface was less resistant. Corrosion protection properties, after removal action and contact with the remover, were evaluate by electrochemical impedance spectroscopy. After approximately 5 hours, coatings were no longer protective due to formation of defects. To simulate the weathering effect, UV-B cyclic test (4 hours of UV exposure followed by 4 hours of saturated humidity at $50^{\circ}C$) were performed for 2000 hours. Gloss and color changes were measured, and electrochemical impedance spectroscopy measurements were performed after aging and graffiti removal.

Keywords

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Fig. 1 Used mask to define the test area for the graffiti simulation.

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Fig. 2 Gloss change after removal cycles using MEK (M) and commercial remover (X) means for the wrinkled surface samples.

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Fig. 3 1W sample after 8 removal cycles using commercial remover.

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Fig. 4 Surface of sample 1S after different UV-B exposure time.

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Fig. 5 Gloss change during UV-B exposure time for the studied samples.

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Fig. 6 Colour change during UV-B exposure time for the studied samples.

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Fig. 7 Impedance diagrams (modulus and phase) of 1S sample at different UV-B exposure time.

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Fig. 8 Impedance diagrams (modulus and phase) of 2S sample at different UV-B exposure time.

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Fig. 9 Coating capacitance obtained from the fitting of EIS data at different UV-B exposure time for samples 1S and 2S.

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Fig. 11 EIS Modulus and phase of sample 1S in function of contact time with commercial remover.

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Fig. 10 Pore resistance obtained from the fitting of EIS data at different UV-B exposure time for samples 1S and 2S.

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Fig. 12. Coating capacitance obtained by fitting EIS data for sample 1S after different time in contact with commercial remover.

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Fig. 13 Coating resistance obtained by fitting EIS data for sample 1S after different time in contact with commercial remover.

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Fig. 14 surface of sample 1S after 10 hours of contact with commercial remover.

Table 1 Studied samples with surface finishing and polymeric matrix characteristics

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Table 2 Number of cycles of graffiti removal effectiveness of the different studied removers

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