A special paint used to make metal surfaces highly resistant to corrosion and penetration of chemical agents. They are widely used in all kinds of equipment to protect them from heavy wear and tear; they are mainly known for their use in military and defense tech owing to the nature of their heavy use.
The Chemical Agent Resistant Coatings (CARC) have been in use for the past several decades, but recent advances in the chemical agent resistant coating technology have opened new doors of possibilities.
The Concept of CARCs
The main component of CARCs is either epoxy-based composition OR polyester-based composition. These specialized coatings are designed to shield the surfaces against potent biological and chemical agents and are commonly used in the Military, Air Force, and Marine Corps.
The major CARCs market regions are North America, Europe, China, Japan, and South Korea. The application process of CARC includes:
- Surface preparation methods
- Top coating
The two types of CARC topcoats are:
Moisture-cure urethane – CARCs made of Moisture-Cure Urethane (MCU) involves combining the isocyanate group with water in a two-stage process to yield a cured paint film. The coating protects from chemicals, sand, and windblown dust. MCU does not emit hazardous air pollutants and comes with a low VOC level.
Water-reducible two-component polyurethane – Water-based CARCs offer high performance and are most used by the military. The coating is composed of water-based polyurethane resins eliminating the need for many solvents like xylene, toluene, etc.
The Need for CARCs
The defense forces are exposed to various arms, ammunitions, and extreme exposure conditions. It results in a high cost of maintaining, repairing, and decontaminating the vehicles and equipment. Also, the forces are exposed to extreme weather conditions.
The need for advanced CARC intensified after Operation Desert Storm in the wake of advanced chemical and biological weapons. Moreover, corrosion is a prime concern in the US Marine Corps (USMC) due to the exposure of the vehicles to harsh conditions, including salty seawater.
The CARCs are used to protect vehicles, equipment, and infrastructure from chemical agents like mustard gas, nerve gas, etc., in combat zones. The coating provides a non-porous finish to the defense vehicles’ surface to shield against radioactive, biological, and chemical weapons. The hazardous elements form beads on the non-porous surface that can be easily washed away. The coating’s effectiveness lies in its chemical repellent or absorption prevention ability.
Advantages of CARCs
The advantages offered by CARC are:
- Offers chemical agent resistance and decontamination
- Enhances the corrosion resistance of the surface
- Matches the IR signature as per the area of operation, thus hindering detection by enemy systems
- Provides camouflage top coatings to reduce visibility in different terrains
- Renders UV resistance to the equipment
- Lowers maintenance cost as the coating is long-lasting
- Improves weather durability and scratch resistance
Disadvantages of CARCs
There are numerous benefits associated with CARCs but with some threats to human health and the environment, if not dealt with correctly. The key to the advantages of CARCs lies in the successful handling of the disadvantages.
The toxicity of CARCs posed a significant threat to Gulf War veterans. The inhalation of CARCs fumes while painting and drying could cause health hazards. The ARL has laid down safety measures while painting, welding, or working with wet CARCs. Dry CARCs do not cause any danger.
The emission of VOCs and hazardous chemicals in CARCs manufacture was a considerable concern until strict regulations were imposed on the VOC emission limit by the US government. Greener technologies are now being developed, keeping in mind the harmful effects of CARCs.
Developments in CARC Technology
CARCs are used in the military since 1985 when the US Army Regulation 750-1 made it mandatory for all tactical equipment. In 2018, the US Army Research Laboratory (ARL) became the approving authority for all CARC products designed for the Department of Defence (DoD) and conducted numerous research in the field.
The US Marine Corps (USMC), in collaboration with Oak Ridge National Laboratory (ORNL), researched the Corrosion Prevention and Control Program (CPAC) on USMC tactical ground and ground support equipment to enhance their life as well as reduce the maintenance need and cost. Under the program, substantial progress was made that exhibited improved corrosion resistance by using Silica-based hydrophobic powder additives on military-grade CARC systems.
The CARC is also applied by the Government Contractors who supply parts and help maintain military vehicles like High-mobility Multipurpose Wheeled Vehicles (HMMWV), Light Armoured Vehicles (LAVs), containers, generators, and shelter exteriors.
From solvent-borne CARCs in the early 1980s to high-performance water reducible CARCs in 2000, the technology is being developed and applied for improving the protection of the expensive military vehicles without harming the environment.
The DoD has issued the following new specifications for vendors:
- Type 1 Coating: CARCs with epoxy-based primer
- Type 2 Coating: CARCs with epoxy-based primer for internal components
- Type 3 Coating: CARCs with camouflage top coatings
- Type 4 Coating: CARCs for ammunition containers
The new environmental norms and safety concerns result in continuous research being conducted in the field, leading to new, better, and safer CARC technology.
In brief, the CARCs, when applied in the correct procedure, offer reduced cost and improved protection for the military. The new technologies in CARCs hold the promise of increased durability with non-photocatalytic material. The technology could be successfully implemented in the industrial and commercial sector in the future on surfaces that are exposed to radiation or chemical toxins.