# Removal of graffiti paint from construction materials coated with TiO2-based photocatalysts

## TL;DR

This study examines how TiO2-based coatings help remove graffiti from construction materials by reducing paint adhesion and aiding in cleaning.

## Contribution

The study evaluates the anti-graffiti performance of TiO2 coatings under real-world conditions using multiple paint colors.

## Key findings

- TiO2 coatings improved graffiti removal effectiveness, especially for certain paint colors.
- Photocatalytic reactions and surface hydrophilicity reduced graffiti adhesion and penetration.
- Cleaning performance varied based on coating properties and graffiti color.

## Abstract

Graffiti on construction materials has significant social and economic impacts, especially on artistic and historical artefacts. Anti-graffiti protective coatings are used to generate low surface energies that limit graffiti adhesion to the surface, thereby reducing surface damage and facilitating removal. The anti-graffiti properties of three commercial TiO2-based coatings were tested under outdoor exposure conditions using four colours of graffiti paint (red, blue, black, and white). Chemical removers were used to clean the stained surfaces to understand the impact of the photocatalytic coatings during the conventional cleaning procedure. The effectiveness of cleaning was assessed by visual observations, colour measurements, and the percentage of residual stain. The anti-graffiti efficacy was strongly dependent on the colour of the graffiti and characteristics of the TiO2 coating. The cleaning performance of TiO2-treated samples was likely related to the photocatalytic redox reactions that decompose the graffiti. Additionally, their hydrophilicity may also prevent the adhesion and/or penetration of graffiti paint on the surface and/or pore matrix.