Introduction to Paints and Coatings
Paints and coatings are applied to various utility items to improve their surface properties such as appearance, adhesion, wetting, corrosion resistance, and wear & scratch resistance. Industrial objects, automotive & transportation, furniture & flooring, architectural surfaces, toys and household goods are some of the examples requiring paints & coatings for protective & decorative purposes.
Paints: Paints are pigmented materials applied on different surfaces as a liquid and dries as a result of several chemical processes to give a thin layer of solid (solid film) on the surface. Paints are usually manufactured, stored, sold, and applied as a liquid. Paints can be water or oil based. Paint typically comprises four components: pigment (provides color), resin (the binder), solvent (the carrier) and additives (property enhancers).
Coatings: Coatings are thin layers of protective materials applied on surfaces to enhance the surface properties such as resistance to corrosion and protection from wear and scratching. Coating is performed through the following processes: (1) Atomic deposition (electrolytic deposition, physical vapour deposition (PVD), chemical vapour deposition (CVD) and plasma deposition); (2) Particulate deposition (thermal spraying, impact plating, enamelling, and electrophoresis); (3) Bulk coating or cladding (painting and dipping, laser cladding, weld overlays, and roll bonding); and (4) Surface modification (anodizing, electrolytic conversion).
Paints and Coatings Testing
Testing paint and coatings is an important step in the evaluation of products and their ability to withstand extreme outdoor conditions. Following are the test types usually applied for testing the protective substances.
- Corrosion testing
- Abrasion and Wear testing
- Ultraviolet exposure and UV testing
- Salt spray testing
- Thermal insulation testing
- Paint and coating adhesion
- Paint and coating film thickness
- Chemical compatibility and resistance testing
- Gravelometer testing
- Thermal cycling
- Autoclave testing
- Volatile organic compounds (VOCs) and semi-volatile OCs (SVOCs) testing
- Flexibility
- Film hardness
- Color and gloss measurements
- Paint or coating deformulation/material identification
- Basic and controlled irradiance spray
- Humidity testing
- Cyclic corrosion
- Immersion testing
- Rotary and vertical dip/dry
- Temperatures up to 260°C (500°F) (ovens) and 1100°C (2000°F) (furnaces)
- Subambient testing to -100°C (-150°F)
- Determination of properties of a liquid paint
- Determination of thickness, gloss and colorimetric parameters of a paint coating
- Cross cut test of a paint coating
- Pull-off test for adhesion of a paint coating
- Impact resistance testing of a paint coating
- Bending test (cylindrical mandrel) of a paint coating
- Pendulum damping test on a paint coating
- Cupping test of a paint coated metal
- Sulfur dioxide test with condensation of moisture (Kesternich test) of coated and non coated steels
- Determination of resistance of a paint coating to water immersion
- Determination of resistance to humidity of a paint coating (one face)
- Determination of resistance to humidity of a paint coating (in cabinet)
- Stone chip impact resistance of a paint coating
- Resistance to xenon lamp exposure (Paint coating and plastic material)
- Scratch resistant test
