Definition of Coating System

A coating system refers to a combination of multiple layers of paint applied to protect steel structures. Each paint layer, with its specific properties, plays a key role in ensuring protection. Industrial coating systems are among the most cost-effective and widely used methods for protecting steel structures, especially storage tanks and refinery facilities, against corrosive atmospheres.

Factors that reduce the lifespan of coating systems include:

• Lack of understanding of environmental conditions
• Unawareness of operational circumstances
• Poor quality of materials and surface preparation
• Improper application of the industrial paint system

Key Parameters for Applying an Effective Coating System:

• Product quality inspection and approval
• Consistent preparation and application of each layer
• Respecting inter-coat drying and curing times

Layers of a Coating System

The table below outlines 6 models of industrial coating systems, including the primer, intermediate, top coat, and protective layers:

Evaluation of Industrial Paint Quality

The paints listed above must be analyzed and tested according to standard procedures. Manufacturers such as Abadgaran must conduct these tests to ensure the quality of their industrial paints. Employers and contractors can refer to these test results to validate the manufacturers' claims.

Curing Time for Coating Systems

The full curing time of a coating system at 23°C and 50% humidity must not exceed 14 days.

Required Tests for Paint Evaluation:

• Maximum sedimentation
• In-can condition
• Pigment particle fineness
• Mixture density
• Pot life
• Percentage and type of main pigment
• Volume solids percentage
• Weight solids percentage
• Abrasion resistance
• Viscosity of the mixture
• Flash point
• Surface dry time
• Full curing confirmation
• Resistance to 100% humidity chamber
• Direct impact
• Indirect impact
• Bending
• Salt spray resistance
• Solvent resistance
• Accelerated weathering resistance
• Paint hardness
• Pigment and resin weight ratio
• Cross-cut adhesion

 Key Considerations in Surface Preparation and Application of Industrial Paints

 Surface Preparation for Coating System Application
One of the essential prerequisites in any painting operation is surface preparation and ensuring a proper substrate condition.

Environmental conditions must be maintained throughout the surface preparation and paint application process—such as ambient temperature.

Environmental Conditions to Observe During Preparation:

• Ambient temperature must be above 4°C and at least 3°C above the dew point
• Surface temperature must be below 50°C and not exceed the paint's thermal tolerance
• Wind speed should not exceed 25 miles per hour (according to SSPC-PA Guide 3)
• Do not perform surface preparation during rain, snow, fog, or storms

Surface Conditions for Coating Application:

Before painting, contaminants such as rust, surface oxides, grease, oil, and any foreign matter must be removed. Also, surface defects such as:

• Sharp edges
• Corner crevices
• Incomplete welds or pinholes must be inspected and corrected. If the surface salt level exceeds ISO 8502-6 or ISO 8502-9 standards, wash the surface with water. Rust can be removed using manual tools, power tools, or dry abrasive blasting (sandblasting).

Cleanliness and Surface Roughness Standards:

The final cleanliness level depends on the type of paint used. For example, zinc-rich epoxy paints require a minimum surface cleanliness of Sa2.5. According to ISO 8501-1, corrosion grades are categorized as A, B, C, and D. If the surface falls into grade A or B, the surface profile must be 30–50 microns. If the surface is grade C or D, the profile depth should exceed 50 microns.

After surface preparation:

• If relative humidity is 70–85% → paint must be applied within 2 hours
• If humidity is below 70% → paint must be applied within 4 hours

Paint Application

For zinc-rich primers:

• Cleanliness: Minimum Sa2.5 (ISO 8501)
• Surface roughness: At least 30 microns, average 50 microns After applying the primer, intermediate and top coats must be applied. Spray application is recommended for large surfaces to achieve a uniform finish.

Selection of Industrial Paints

In any coating system, the primer, intermediate, and top coats must be selected together. For example:

• Primer: Zinc-rich ABADUR 201
• Intermediate: Epoxy ABACOAT PM-11
• Top Coat: Epoxy ABADUR HP-350 For polyurethane-based systems: ABACOAT PUR-40 as the top coat

Curing and Drying Time

The coated system must cure for at least one week after the top coat is applied. During this time, the surface should not be used.

Layer Thickness in Coating Systems

The total thickness of the applied layers must follow the manufacturer’s guidelines. It must not be less than the recommended thickness, and a deviation of up to 20% above the recommendation is allowed. Adequate thickness enhances durability and protection.

Thinner and Viscosity Adjustments

To achieve optimal viscosity, thinners may be used. Based on the paint type, appropriate amounts can be added. Tools such as spatulas or dip viscometers can be used for measurement.

Note that adding thinner affects the volume solids percentage. Therefore, solids content must be recalculated. To achieve the desired dry film thickness, wet film thickness must also be recalculated.

This is a critical part of the painting process to ensure proper performance and longevity of the coating system.