Identifying And Preventing Corrosion Problems

Corrosion, a Worldwide Enemy

Corrosion is the constant enemy to man-made structures. Many industries and most governments face some type of threat. The World Corrosion Organization reports that the U.S. cost of corrosion is $2.2 trillion and 3% or more of global GDP.

Corrosion causes a breakdown of physical, chemical and mechanical properties over time. Consequently, the threat comes from deterioration that can lead to countless environmental hazards, injury, death, and/or profit loss, including work stoppage, recall, fines and expensive repairs.

Understanding Corrosion

Concrete, wood, and metal substrates (especially iron) are particularly vulnerable to deterioration. Typically, corrosion is caused by the passage of time and some outside trigger. The catalyst may involve one or many factors such as moisture, chemicals, salt, gas, microbial elements, electrochemical reactions, movement (friction or impact), humidity (wet or dry) and temperature (excessive cold, heat or freeze/thaw cycles.

Indications of corrosion often start with visual signs of rusting, pitting, cracking, softening, peeling or reduction in material thickness and strength. Eventually, the deterioration process shows more hazardous indications such as leaks, crumbling, contamination or structure collapse.

Battling Corrosion with Prevention

The main tools for fighting corrosion are coatings and linings. The purpose of using a coating is to form a protective barrier before corrosion starts. This generally involves some type of surface preparation, a primer to ensure adherence and the coating. A decorative topcoat may also be applied.

There are many cautions in selecting the right materials for the job. These factors include:

Projected Lifespan: rubber lining, paint and other products designed to protect surfaces simply do not last as long as polymers such as ArmorThane’s polyurethane and polyurea.
Cross-contamination: some materials can release and absorb materials causing contamination.
Chemical elements: reactants and corrosive materials sit harmlessly against a polymer barrier while chemically aggressive fluids will find and exploit weaknesses found in rubber linings, epoxy and paint.
Abrasion/Impact: some products do not have the same abrasion and impact resistance as polyurethane or polyurea. Polyurea particularly is the best coating for underground pipelines where the ground shifts or on bridge girders exposed to vibration.
Surface Design: unlike pre-formed liners, sprayed-on coatings are thinner and take up less space. They form a seamless membrane that exactly fits the shape, even where poles, pumps and other internal or external structures attach. Penetrations such as piping and drains are sealed by a spray polymer so that even vibrations do not cause an unexpected leak.
Environmental Extremes: ArmorThane coatings are not damaged by constant exposure to direct sunlight or freeze/thaw cycles. Surfaces expand and contract without cracking in extreme weather. Some products must be applied in perfect conditions while we have coatings that can be sprayed in a wide range of temperatures and humid/moist environments.

We realized a long time ago that diverse corrosive conditions required different coating properties. If not carefully selected and professionally applied, the protective barrier can fail possibly causing worsening outcomes.

Here are some considerations in selecting the best polymer for the job:

Remember, prevention is better than repair.
The surface preparation will be different depending on if the project is prevention or repair.
What is the severity of deterioration? Not everything can be repaired by coating.
What type of surface is being preserved? The type of coating, primer and preparation steps will differ to prevent delaminating.
What is the nature of the corrosive environment and is it a temporary or ongoing problem? Some problems can be helped by fixing an underlying cause such as a water leak or soil buildup. Others need a specialized coating to fight ongoing exposure or abuse.
What is the risk associated with corrosion? Looking bad versus extreme danger may drive coating selection and application.
What is the length of time expected/desired between repairs? Some decisions may alter the type of coating and application depending on the ease of inspection and repair. Sewers, for example, may be difficult to reach and hard to repair therefore requiring maximum coating.
How important is it to create a barrier? Liquids and gases that can permeate cracks and crevices require a leak-proof membrane. If the surface has only one side exposed, only that side may need coating again wind, friction or impact.

ArmorThane has developed several polymer coatings including pure and specially-formulated hybrid polyurea and polyurethane products, depending on the substrate and threat. They are cost effective, flexible and, most importantly, work well for years. Many of our products are less expensive than comparable epoxy coatings with better durability and are far superior to paint.