Military Coating Standards

What is Defense Industry?

Defense industry can be described as the sector that provides the production of tools and equipment necessary in the national defense field. More specifically; every country that has declared its borders must protect those borders to ensure its continuity. In order to protect their borders, countries must have not only an army consisting of manpower that can directly protect or utilize necessary equipment, but also possess the required tools and equipment for all these purposes. While the defense industry sector constitutes a large part of the economy in developed countries, in less developed countries it is among the sectors to which resources are allocated and development is prioritized. Defense industry is also quite important for countries to ensure their continuation in security and prosperity. Today, the countries with the most advanced defense industries are the United States, Russia, China, the United Kingdom, and Israel – countries that are highly developed economically and strategically positioned due to their political status. Important work is also being carried out in our country in terms of producing basic defense industry requirements. The United States is at the forefront of countries manufacturing military equipment, and has developed special coating standards to protect military vehicles from corrosion, calling them MIL STD. In this article, we will discuss MIL (Military Standard) Standards and CARC coating, a special military coating.

The U.S. Department of Defense uses a U.S. defense standard frequently referred to as "MIL-STD", "MIL-SPEC" or (outside official terminology) "MilSpecs" to achieve standard objectives. Detailed specifications on how a specification should be archived are linked to standards via MIL-DTL.

  Standards are used to enable collaboration, meet specific requirements of products, ensure their reliability and stability, manage total costs, compliance with logistics systems, and meet objectives relating to similar characteristics. Defense standards are also used by other defense government organizations, technical organizations, and industry organizations. In the defense industry, paints and coatings play a major role in preventing corrosion. Paints manufactured in accordance with these standards and applied within standard guidelines possess numerous qualities such as corrosion prevention, reduction of material damage, and fire protection. Some of the MIL-DTL specifications are as follows. MIL-DTL-14072 This specification covers the requirements of final finishing processes necessary to protect ground electronic equipment from the adverse effects of climate conditions encountered in military use. MIL-DTL-15090 This specification covers coating compatible with volatile organic compounds (VOC) of up to 250 grams per liter (maximum) (2.08 pounds per gallon). The paint is a light gray equipment enamel for use as a final coating on equipment, machinery, furniture, and electrical equipment such as electrical panels used aboard ships.

This product can be used wherever VOC air pollution regulations apply. The light gray equipment enamel within the scope of this specification is an air-dry, solvent-based coating for use in all interior dry areas, including applications covered by reactor facility painting programs. This product is supplied in a single container and is used without dilution.

  MIL-DTL-24441 This specification covers a series of two-component epoxy-polyamide paints designed to protect surfaces against environmental hazards. MIL-DTL-24607 This specification covers semi-gloss, chlorinated alkyd resin enamel for use on primed, smooth metal, glass-reinforced plastic (GRP), wood, and plastic/composite surfaces that do not support flame or flashing when dry. MIL-DTL-24631 This specification covers requirements for two-color camouflage paint and flexible white marking paint. MIL-DTL-53022 This specification covers a quick-dry, corrosion-preventing epoxy primer for ferrous and non-ferrous surfaces. The primer is lead-free, chromate-free, and meets air pollution requirements for solvent emissions. MIL-DTL-5303 This specification covers a single-component, polymeric leveled, chemically-resistant, aliphatic polyurethane coating for use as a final coat on military tactical equipment including ground coating, aircraft, and related support assets. Except as specified, materials are free from inorganic hazardous air pollutants (HAPs) other than cobalt and non-hexavalent chromium, and from volatile organic hazardous air pollutants (HOCs). The coating contains no lead, cadmium, cadmium compounds, or hexavalent chromium. Free from volatile organic hazardous air pollutants (HOCs). MIL-DTL-53072 This specification covers requirements related to the application and inspection of CARC systems used in military equipment. It is required for use in the selection process of appropriate materials and procedures for surfaces to be coated and provides additional application, inspection, and quality control information for cleaning, pre-treatment, and coating characteristics referenced in tables. Paint Applications with MIL Standards With developing technology in view of these standards, fuel tanks of vehicles used in military institutions are coated with paint containing flame-resistant polyurethane and special intumescent super-absorbent polymer designed to minimize or prevent fuel tank leakage due to low-intensity armed fire. Intumescent super-absorbent polymer works together with polyurethane to seal unwanted entry and exit holes created by a bullet.

Paint Applications with MIL Standards

With developing technology in view of these standards, fuel tanks of vehicles used in military institutions are coated with paint containing flame-resistant polyurethane and special intumescent super-absorbent polymer designed to minimize or prevent fuel tank leakage due to low-intensity armed fire. Intumescent super-absorbent polymer works together with polyurethane to seal unwanted entry and exit holes created by a bullet.

One of the fire protection paint applications carried out for safety is a modified epoxy binder filled with thermally active materials that produce cooling gases when exposed to temperatures above 350°C. This high-heat-resistant coating can withstand sustained temperatures above 1000°C and can withstand explosions up to 5000°C. This coating can be used in both military and commercial applications.

CARC Coatings

CARC (Chemical Agent Resistant Coating) is a two-component polyurethane paint that has been used since 1985 as a final coat on military war materiel, military vehicles of all armed services, aircraft, ammunition, and tactical equipment. CARC is designed to be easily cleaned after exposure to liquid chemicals and additionally the coating is resistant to water, air conditions, hydrocarbons, and acids. The coating contains an infrared signature that makes the coated equipment difficult to detect. Component A is a polyester resin, and Component B is an aliphatic isocyanate curing agent.

The CARC system is a combination of pre-treatments, primers, and final coats. After surface preparation and pre-cleaning, the exterior surfaces of vehicles are painted with an epoxy primer, followed by an aliphatic polyurethane final coat. The interior of hull-type vehicles is coated with an epoxy enamel over the epoxy primer.

CARC resists corrosion and chemical agent penetration. It does not absorb chemical agents like alkyd paint. At the same time, it is resistant to removal with pollutant cleaning solutions.

Chemical-resistant coating (CARC) contains isocyanate (HDI), which greatly irritates the skin and respiratory system. High concentrations of HDI can cause itching and redness symptoms, burning sensation in the throat and nose, and eye watering. At excessive concentrations, HDI can cause coughing, shortness of breath, pain during breathing, increased sputum, and chest tightness. When CARC paint is used, the following precautions must be taken:

  • Always wear a respirator when using CARC paint unless air sampling shows a rate below standards. If air sampling is below standards, use a filtered respirator. • Protect skin or eyes from contact with CARC paint. Always wear protective equipment (gloves, mask, safety glasses, etc.). • Ensure adequate ventilation when applying CARC paint. • Mixed CARC is extremely flammable. Use only in well-ventilated spaces. Keep away from flames, sparks, and other fire sources. • Do not use CARC on components such as manifolds and mufflers exceeding 400°F. Equipment may be damaged by toxic fumes. • Never weld or cut materials coated with CARC. • Do not sandblast CARC-coated equipment without using high-efficiency air-cleaning respiratory devices. • If exposed to CARC paint, be aware of possible symptoms; symptoms may appear several days after initial exposure. If symptoms are detected, seek medical attention immediately. • Unused (CARC) mixtures are considered hazardous waste.

Usage Notes:

• CARC colors should not be mixed with each other, as this will alter individual effectiveness when applied to the final product. • Do not use CARC on flexible components. Due to its hardness, it may crack when bent. • Do not use CARC on rubber, lacquer coatings, or vinyl. • CARC is not used on materials containing anodized or parkerized surfaces (such as weapons). • CARC is not used as a final coat on wood. Wood expands and contracts with air changes. CARC is not flexible enough to move with wood, so it can crack and peel. As a result of the Clean Air Act and 1990 amendments, federal and local regulations limit the amount of VOC (volatile organic compounds) released during surface coating application. In response, the U.S. Army Research Laboratory Coating Research Team developed a formula with lower VOC content that creates water-dispersible CARC (WD CARC). This new formulation is lead and chromium-free, and is more resistant to wear and scratching.

Water-Based CARC:

• Contains water and is thinned with water. • The solvent content of WD CARC is half that of solvent-based CARC. It also contains no hazardous air pollutants. • Fully compatible with all existing CARC primers and final coats. • More flexible after application. • More durable and does not scratch as easily as old CARC. • Much more durable in all weather conditions. • Does not fade like old CARC. • Personal protective equipment required during spray and brush application is the same as with solvent-based CARC.

Typical CARC Applications:

• Space / Aerospace: Combat and Transport Aircraft, Combat Vehicles. • Battlefield and Transport Vehicles. • Support Equipment, Radar Installations. • Tactical Combat Ship Equipment. • Maritime / Warship: Corrosion resistance in salt water environments. • Military Equipment: Protection against corrosion and wear resistance.

References:

1) https://en.wikipedia.org/wiki/United_States_Military_Standard 2) https://www.steelconstruction.info/Paint_coatings#Etch_primers 3) https://www.microsurfacecorp.com/coating_solution_military.php 4) https://blog.pasternack.com/uncategorized/difference-mil-std-mil-hdbk-mil-dtl-mil-prf-mil-spec/ 5) http://everyspec.com/ (https://www.hit-usa.com/battlejacket.php 6) https://www.qp-c.com/defense-military-1 7) Olive-Drab, About the Original CARC Paint, Accessed: 5 February 2018, http://olive-drab.com/od_mvg_camo_carc2.php 8) Inetres, Chemical Agent Resistant Coating (CARC), Accessed: 5 February 2018, http://www.inetres.com/gp/military/cv/carc.html 9) Elekcrolurgy, CARC (Chemical Agent Resistant Coating) Paint, Accessed: 5 February 2018, https://electrolurgy.com/processes-services/carc/   Seda Ömercikoğlu Yüce, MICorr, PCS General Manager NACE Senior Corrosion Technologist STM Coatech