How to formulate corrosion resistant coatings?

Corrosion means degradation of a material caused by chemical or electrochemical reaction with the environment. The material generally refers to metals but can also include non-metallic materials, such as ceramic, polymer and plastics. Corrosion not only affects the strength and durability of a material but also proves to be expensive.

There are two pre-requisites for your coating to exhibit corrosion resistant properties:

• Good film formation through proper coalescence such as in waterborne 1K: A well-formed film acts as a barrier between the underlying substrate (the material being protected) and the corrosive environment. Good coalescence creates a continuous, dense film with minimal gaps. This significantly reduces the permeability of the coating, making it harder for corrosive elements to penetrate.

• Adequate cross-linking such as in 2K systems and baking enamels: A well-cross-linked network creates a denser film with smaller voids. This significantly reduces the permeability of the coating, making it harder for corrosive agents like water, oxygen, or salts to seep through and reach the metal substrate.

• Adhesion: Strong adhesion ensures the coating remains firmly in place, maximizing its effectiveness as a barrier and protecting the metal from direct contact with corrosive elements

It is essential to note that enhanced barrier properties also lead to improved water resistance. The strategy of an anticorrosive coating is to break the circuit of electron flow. It provides a barrier to water, electrolytes and oxygen to prevent electrochemical cells from forming.

Note: High degrees of cross-linking can lead to brittle films and poor adhesion, flexibility, and impact resistance. So, look for these trade-offs.