Protective coatings for corrosion control

The industrial, commercial, and architectural markets rely heavily on coatings for the protection of assets. In a general sense, coatings are defined as a thin layer of solid material on a surface that provides improved protective, decorative, or functional properties. More specifically, they are a liquid, liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective, decorative, or functional adherent film. Protective coatings are applied to a surface to protect the substrate from corrosion. An effective way in which to protect metal from corrosion is by physical isolating a substrate from its environment by applying protective coatings.

Coatings protect against corrosion through one of the following ways: they block necessary elements from coming to together to start the corrosion process, actively prevent the electrochemical reaction from occurring, or steer the corrosion process in a direction that is will not harm the asset.

Also see protective coatings learning center

Quick facts

Types of coating protection include: 

• Barrier -- Protect by preventing water, oxygen, and electrolytes from contact with an underlying metal
• Inhibitive -- Coatings that contain chemicals that work to hinder corrosion
• Sacrificial -- Thin metal layers that have lower electrode potential values or those having higher levels in the electrochemical series are applied
• Combination

Materials typically used in protective coatings are:

• polymers, epoxies, and polyurethanes for non-metallic coatings
• zinc, aluminum, and chromium for metallic coatings 

Application

Coatings, which includes paints, can be:

• sprayed
• welded
• plated, or
• applied with hand tools (specific to the surface, environment, and application goals)

The process for applying protective coatings involves:

• surface preparation
• application of a primer
• a full coating
• use of a sealant

For information specific to “Coatings Inspection” see section titled measurement and inspection