Investigating tribological properties of electrophoretically deposited graphene nanoplatelets coatings on mild steel

The use of graphene-based materials to enhance the tribological properties of metal surfaces has garnered increasing interest in recent years. In fact, various studies have demonstrated that graphene-related materials, such as graphene nanoplatelets (GNPs), hold promise as solid lubricants. Electrophoretical deposition (EPD) is an interesting coating method to obtain a deposition of particles such as graphene as it is a simple, cheap and effective process with a low environmental impact. This study focusses on investigating the tribological properties of GNPs coatings obtained through anodic EPD on mild steel. Specifically, a combination of GNPs and deionized water as the deposition medium is introduced, allowing a cost-effective process with reduced environmental impact. Deposition time (5, 10 and 20 min) and concentration in the bath (0.5, 1 and 1.5 g/l) were varied in a full factorial plan to highlight their effects on coating performance. The coatings achieved demonstrated good adhesion with scratch break loads above 10 N and excellent tribological performances, with a friction coefficient of above 0.1. The results showed how concentration and process duration have two opposing effects on the adhesion and tribological characteristics of the coatings. The presence of an intermediate optimal condition, with 10 min deposition and a GNP concentration of 1 g/l, leading to an improvement in anti -wear properties of approximately 85 % and a coating break distance of over 80 m. An ANOVA analysis was developed to confirm the statistical significance of the process parameters in adhesion and tribology of the coatings.