We are trying to coat our material over pure aluminium sheet. but due to hydrophobic nature we are unable to achieve desirable coating. Any suggestion?
The suface properties of (on a micro scale clean) high energy surfaces like that of metals and oxides are largely determined by adsobates from the surrounding atmosphere. These adsorbed layers contain water and also hydrocarbons. The latter are responsible for the high contact angle of water. Removing these hydrocarbons is the way to go in order to obtain a hydrophilic surface.
There are many different ways of doing that. Ozone cleaning or etching as stated before. Others might be solvent cleaning possibly supported by ultrasound, plasma treatments etc.