How does Moisture Degradation Occur in Paints?

Here is the step-by-step process of how moisture penetration degrades the paint:

1. Swelling of Paint Film: Moisture crosses the protective barrier of paint through a hole or crack. It gets trapped on the substrate with air and does not evaporate. This moisture penetration affects the freeze-thaw cycles and chemical bonds of paint. Paint film loses its adhesion and swells after these structural changes. 
2. Microbial Growth: Microorganisms feed on the carbon sources from linseed oil, alkyd resins, and casein. Cellulose-based thickeners are a food source for fungi due to their organic nature. These paint formulations promote the growth of microbes, which pushes the paint layer away from the substrate.
3. Chemical Degradation: Moisture interacts with paint formulations and changes their viscosity. It starts to peel off like chalk and powder. High moisture level affects the color, strength, and the ability of the paint to resist weather changes. 

How Does Moisture-Resistant Paint Work?

Here is how moisture-resistant paints work:

1. Hydrophobic Formula: Moisture-resistant paint contains water rippling additives and binders such as fluorocarbons, silicones, fluorine-free repellents (eco-friendly alternative of fluorocarbons), aluminium-free salts, and waxes. These additives do not let the water reside on the substrate like a droplet that moves in oil-based paints. 
2. Tight Film Formation: Moisture-resistant paints leave a strong film after solvent evaporation to resist UV radiation and moisture. Flat, matte, and eggshell finishes are not suitable for moisture-prone areas as they absorb water and cause damage. 
3. Breathable Barrier: Moisture-resistant paints allow air exchange and block the external water from penetrating the substrate. Unlike latex and acrylic, which are composed of plastic components, moisture-resistant paints contain lime, clay, and mineral pigments in their formulation.
4. Anti-Mold & Mildew Additives: Moisture-resistant paints contain fungicides such as carbendazim, iodopropynyl butyl carbamate (IPBC), zinc pyrithione, and mitbenzisothiazolinone. Manufacturers also use tea tree oil and citrus seed extract as an alternative to resist mold growth. 
5. Durability Boosters: Moisture-resistant paints composed of cross-linking polymers do not deteriorate and fade easily. They contain UV stabilizers, absorbers, and thickeners, which increase the strength and lifespan of paint film.

What Are the Types of Moisture-Resistant Paints?

Here are the six types of moisture-resistant paints:

1. Acrylic Latex Paints: Acrylic latex paints contain acrylic polymers and water as a primary solvent, which vaporizes quickly. It resists moisture to an extent, depending on the type of resin used in formulation. Acrylic latex paints are not fully waterproof, as they are prone to damage in highly humid environments. Choose the silicon-based resins to achieve a moisture-resistant and durable finish. It is used in the kitchen, bathroom, storage spaces, near tubs, and shower walls to prevent mildew growth.
2. Silicone-Based Paints: Silicon-based paints contain silicon resins that are water-repelling components. It does not hold the moisture on the surface and has a breathable film. Silicon-based paints provide a flexible and durable finish to facilitate freeze-thaw cycles. Most common types of silicon-based paints include silicone masonry paints for masonry, silicone-modified acrylic paints for concrete, industrial silicone coatings for storage tanks, and SILOTEX for decorative purposes.. It is used to paint shipping vessels, concrete walls, and automotive parts. 
3. Epoxy Coatings: Epoxy coatings do not soak up water due to their non-porous nature. They contain a hardener in a two-component epoxy coating, which creates a thick protective barrier against environmental factors. The most common types of epoxy coating are powder coatings, 100% solids, water and solvent-based. Epoxy coatings are used to paint garages and industrial equipment due to their highly water-resistant characteristics.
4. Elastomeric Paints: Elastomeric paints contain acrylic polymer, which forms a thick protective layer to allow contraction. It is not prone to cracks due to its rubber-like film. Elastomeric paints prevent cracks and moisture from penetrating brick and stucco walls.  
5. Oil-Based Alkyd Paints: Oil-based alkyd paints are less resistant to water compared to silicon-based paints. It is due to the type of resin and less breathable surface that causes bubbles, yellowing, and orange peels. Oil-based paints are non-polar, yet they absorb water as the lipases and esterases enzymes of fungi break these bonds and make them prone to tearing and wear.
6. Mildew-Resistant Paints: Cement, polyurethane, satin, and semi-gloss paints contain antimicrobial agents that minimize the growth of microbes. These mildew-resistant paints are used to paint laundry rooms, plant pots, gates, and fences. 

How to Choose the Right Moisture-Resistant Paint

Here is how to choose the right moisture-resistant paint:

1. Consider the Surface Type: Understand the substrate texture, its ability to hold the paint, and the impact of environmental factors before making a purchase. Selecting water-based paints for building exterior increases future expenses. Plaster walls, concrete deck, and metal equipment require a different type of paint to resist moisture. 
2. Check for Label Claims: Look for the paint cans with “moisture-blocking”, “bathroom safe”, “mildew-resistant”, and “waterproof” labels. Read the instructions or user guide, as washable, scrubbable paint often has water-resistant capabilities.
3. Gloss Level Matters: High gloss paints have a high refractive index due to titanium oxide and zinc oxide pigments. It reflects light at an incident angle and does not allow UV and heat to pass through it. Unlike matte paints that have a porous surface, high gloss paints block the entry of water due to their non-porous surface.
4. Indoor vs. Outdoor Use: Outdoor and indoor use have different paint requirements due to environmental exposure. Indoor requires quick drying, low VOC, and moisture-resistant paints. Replace the dry walls with dense armor, install a ventilation system, and opt for the right type of paint for a high high-moisture bathroom area. Home exteriors demand a UV-resistant, water repellent, and heat-proof paint.
5. Primer Compatibility: Choose the primer based on the surface type (meta, stucco, concrete). Most commonly used primers are epoxy primer, bitumen, red oxide, acrylic emulsion, and acrylic cement. They improve the paint adhesion and create a barrier against moisture. 

What are the Application & Maintenance Tips for Moisture-Resistance Paint

Here are the application and maintenance tips for moisture-resistant paints:

1. Prepare the Surface: Remove the residues, dirt, and mites from the substrate before paint application. Choose the right tool (brush, roller), application technique, and paint type to achieve the desired results. 
2. Use Primer: Use primer to activate the surface and enhance paint adhesion. Paint falls and peels away quickly without primers. Apply water-sealing primers that breathe and block the external moisture.
3. Apply Two Coats: Multi-coat paint to cover the satin and ink marks. These high-opacity finishes increase the durability and water-resistance of paint. It also provides a uniform coverage and aesthetic appeal to the substrate. 
4. Recoat as Recommended: Repaint the substrate after 5-7 years to maintain its water-resistant abilities. Fill the dents, cracks, and peeled paint with a fresh mixture. Neglecting the repainting recommendation leads to increased future expense and the risk of water damage to the substrate.
5. Ventilation is Key: Highly humid regions with less ventilation promote the mildew growth. Install exhaust fans or dehumidifiers to vaporize the moisture and limit mold growth. Proper ventilation aids in the quick drying and curing of paint. It reduces the amount of volatile organic compounds in the air to minimize allergy and respiratory disorders.