Water based coating composition for wind blades

A wind blade comprising a substrate having an outer surface, wherein at least a part of the outer surface is coated with a multilayer system comprising

• A) a putty layer applied on the outer surface of the substrate;
• B) a primer layer applied on the putty layer;
• C) at least one coating layer, wherein the at least one coating layer is formed from a coating composition comprising:
• a) a primary composition comprising one or more aqueous dispersions of an aliphatic polyurethane;
• wherein said one or more aqueous dispersions has a particle size characterized by a D50 (median) value below 1000 nm;
• and
• b) a secondary composition comprising one or more polyisocyanates;
• wherein
• said one or more aqueous dispersions in a) is present in an amount of at least 5 times the amount of said one or more polyisocyanates in b) based on weight;
• and
• D) a leading edge protective coating layer covering at least a part of the wind blade,
• wherein the wind blade is a wind turbine blade.

A method for protecting a wind blade against erosion, comprising a step of applying a coating composition comprising:

• a) a primary composition comprising one or more aqueous dispersions of an aliphatic polyurethane;
• wherein said one or more aqueous dispersions has a particle size characterized by a D50 (median) value below 1000 nm;
• and
• b) a secondary composition comprising one or more polyisocyanates;
• wherein
• said one or more aqueous dispersions in a) is present in an amount of at least 5 times the amount of said one or more polyisocyanates in b) based on weight;
• wherein the coating composition is applied on at least a part of an outer surface of said wind blade and allowing film formation to take place, thereby forming at least one coating layer that protects the wind blade against the erosion,
• wherein the wind blade is a wind turbine blade.