Pre-treatment coating composition and a method for producing the same

A method for producing a pre-treatment coating composition for a metal substrate, the method comprising the steps of:

• i. subjecting a graphite ore to an electrolytic treatment to obtain an expanded graphitic material;
• ii. subjecting the expanded graphitic material to an exfoliation treatment to obtain single-layer graphene and few-layer graphene, wherein the exfoliation treatment is a combined chemical and high-pressure treatment comprising intercalating the graphitic material with an intercalating agent and a surfactant in an intercalation step and subjecting the intercalated graphitic material to a high-pressure homogenisation treatment;
• iii. separating graphene obtained from the exfoliation treatment from any residual graphitic material;
• and
• iv. functionalising the graphene with a coupling agent for coupling graphene to the metal substrate;
• wherein the electrolytic treatment is carried out in the presence of an electrolyte that comprises ammonium ions and sulphur-containing ions and the sulphur-containing ions are separated from the expanded graphitic material by mixing the expanded graphitic material with a liquid that is immiscible with water.