Coating Building Materials Requires More Than Choosing a Building-Material Paint

When coating building materials, first identify what is to be coated.

Is it metal?
Is it wood?
Is it concrete?
Is it mortar?
Is it aluminum?
Is it galvanized steel sheet?
Is it an inorganic board material?

The term building materials covers a very diverse range of substrates.

Even for the same material, the required coating film performance changes with the location of use.

Will it be used outdoors?
Will it be used indoors?
Will it get wet in the rain?
Will it be exposed to ultraviolet radiation?
Is it flooring that people walk on?
Is it furniture that people touch?
Will it be used in a coastal area?
Will it contact chemicals or oil inside a factory?

Paint selection, pretreatment, film thickness, drying conditions, and inspection items change with these conditions.

In coating building materials, simply using a paint intended for building materials is therefore insufficient.

What matters is working back from the material and service environment to determine the necessary coating film functions.

Main Coating Film Functions Required for Building Materials

Coating films on building materials need to provide various functions.

Typical examples are as follows.

• Preserving appearance
• Prevent rust
• Protecting the substrate from rainwater
• Reducing deterioration caused by ultraviolet radiation
• Preventing moisture-related blistering and peeling
• Resisting abrasion and scratches
• Make the surface resistant to soiling
• Making cleaning easier
• Reducing absorption and cracking in wood
• Accommodating moisture and alkalinity in concrete
• Meeting flame-retardant or fire-protection requirements where necessary

The functions required differ with the product’s application.

For exterior wall materials, weather resistance, waterproofing, and resistance to soiling are important.
For metal components, corrosion protection and weather resistance are important.
For flooring, abrasion resistance and ease of cleaning are important.
For furniture materials, decorative appearance, feel, and scratch resistance are important.

When coating building materials, first clarify what the coating is intended to protect in this product.

Corrosion Protection and Edge Treatment Are Important for Metal Building Materials

Corrosion protection is important for metal building materials.

Iron and steel rust when exposed to moisture and oxygen.
When used outdoors, they are affected by rain, moisture, ultraviolet radiation, salts, and airborne pollutants.

In Vietnam in particular, attention is needed to high temperature and humidity, the rainy season, and salt exposure in coastal areas.

Rust-prone areas on metal building materials are not limited to flat surfaces.

The following locations are particularly vulnerable.

• Edges
• Cut edges
• Drilled holes
• Welded areas
• Bent areas
• Around bolts
• Scratched areas
• Areas where water tends to collect

Even if the coating on a flat surface looks good, rust begins at edges or cut surfaces if their treatment is insufficient.

Coating metal building materials requires checking pretreatment, film thickness, edge treatment, and repair methods, as well as paint type.

Galvanized Materials and Aluminum Are Not Necessarily Easy to Coat

Galvanized steel sheet and aluminum are also used for metal building materials.

They may have better corrosion resistance than iron.
However, that does not mean they are easy to coat.

Adhesion on galvanized materials changes with surface condition.
Residual white rust, oil, surface treatment agents, or contamination from storage can lead to poor coating film adhesion.

For aluminum, the surface oxide film and pretreatment conditions are important.
When used outdoors or in coastal areas in particular, both corrosion resistance and decorative appearance need consideration.

Aluminum is unlikely to develop red rust, but it is not immune to corrosion or deterioration in appearance.

When coating galvanized materials or aluminum, check the following points.

• Substrate surface condition
• Whether oil or white rust is present
• Type of surface treatment
• Whether a primer is needed
• Adhesion to the paint
• Whether use is outdoors or indoors
• Whether use is in a coastal area

Rather than assuming a rust-resistant material will be fine, select pretreatment and coating specifications suited to the substrate.

Moisture Content and Absorption Are Important for Wooden Building Materials

Wood is a completely different material from metal.

Moisture management is the first important consideration in wood coating.
Wood absorbs and releases moisture.
This characteristic can lead to cracking, blistering, peeling, or discoloration of the coating film.

Coating wood with a high internal moisture content can lead to later moisture release, causing coating film blistering or peeling.

Checking moisture content is therefore important in wood coating.

Moisture content is the proportion of moisture contained in the wood.
If it is not managed properly, problems may recur even after changing paint.

Wood also absorbs paint.
Uneven absorption causes variation in color, gloss, and finish.

Wooden building materials require the following checks.

• Is the moisture content appropriate?
• Is surface sanding sufficient?
• Is absorption uniform?
• Is a primer or sealer needed?
• Is it for indoor or outdoor use?
• Will it be exposed to direct sunlight or rain?
• Can the coating film accommodate wood expansion and contraction?

Wood coating requires flexibility to accommodate wood movement, as well as coating film hardness.

Cracking on Wood Is Not Solely a Paint Problem

Cracking is a common problem in wood coating.

The coating film surface may crack, or cracks may occur because the coating cannot accommodate movement of the wood itself.

Wood expands and contracts with temperature and humidity.
It swells when absorbing rainwater or moisture and shrinks when it dries.

Large movements place stress on the coating film.

Causes of cracking include the following.

• High wood moisture content
• Insufficient drying
• An excessively hard coating film
• Excessive film thickness
• An unsuitable primer
• Uneven paint absorption by the wood
• Outdoor exposure to ultraviolet radiation and rain
• Large environmental changes after installation

Treating cracking in wood coatings solely as a paint problem is therefore insufficient.

Wood properties, moisture content, surface treatment, coating film flexibility, and service environment need to be checked together.

Pay Attention to Moisture and Alkalinity in Concrete and Mortar

Coating concrete or mortar requires different precautions from coating metal or wood.

Moisture and alkalinity are particularly important.

Concrete and mortar retain moisture for some time after placement.
Coating before sufficient drying can cause blistering, peeling, or whitening of the coating film.

Concrete and mortar are also alkaline.
If the paint has poor alkali resistance, the coating film may deteriorate or discolor.

The following checks are important when coating concrete or mortar.

• Has sufficient curing time been allowed after placement?
• Is the moisture content appropriate?
• Is the surface alkalinity acceptable?
• Have laitance and powdery layers been removed?
• Have cracks been repaired?
• Is the primer appropriate?
• Is waterproofing needed?
• Whether use is outdoors or indoors

Laitance is a weak layer that forms on the concrete surface.
If it remains, the coating film may not adhere firmly.

Concrete may still contain internal moisture even when its surface looks dry.
Avoid judging by appearance alone and check moisture conditions as necessary.

Abrasion Resistance and Slip Resistance Are Important for Flooring

Among building materials, flooring is subjected to particularly severe loads.

People walk on it.
Carts travel over it.
Goods are placed on it.
It is cleaned.
Water or oil spills on it.
In some cases, it is also exposed to chemicals or heat.

Floor coatings therefore require abrasion resistance, as well as appearance.

Abrasion resistance is the ability of a coating film to resist wearing away through rubbing or friction.

Flooring may require the following properties.

• Abrasion resistance
• Water resistance
• Chemical resistance
• Oil resistance
• Slip resistance
• Ease of cleaning
• Stain resistance
• Ease of repair

However, roughening the surface to increase slip resistance may make dirt more likely to remain.
Conversely, smoothing the surface to improve cleaning may make it more slippery.

Floor coatings need a balance of abrasion resistance, ease of cleaning, and safety appropriate to the location of use.

Outdoor Building Materials Need Resistance to Ultraviolet Radiation and Rainwater

Weather resistance is important for building materials used outdoors.

Weather resistance means the ability to withstand outdoor conditions.
It refers to resistance to coating film deterioration caused by ultraviolet radiation, rain, moisture, temperature changes, and airborne contamination.

Common problems with outdoor building materials include the following.

• Fading
• Discoloration
• Gloss loss
• Chalking
• Cracking
• Blistering
• Peeling
• Rust
• Dirt deposition
• Reduced waterproofing performance

Chalking is deterioration of the coating film surface that leaves a powdery appearance.
It is a common form of deterioration in outdoor coatings.

For outdoor building materials, consider how the coating will deteriorate after several years, as well as its beauty immediately after application.

Stain Resistance and Ease of Cleaning Are Important for Indoor Building Materials

Building materials used indoors may experience less severe ultraviolet radiation and rain than those used outdoors.

However, indoor use has its own requirements.

For example, the following properties are important for wall materials, furniture, shelving, doors and fittings, and interior panels.

• Decorative appearance
• Feel
• Stain resistance
• Ease of cleaning
• Scratch resistance
• Resistance to yellowing
• Low odor
• Safety
• Meeting flame-retardancy requirements where applicable

People often look closely at and touch indoor building materials.
Fine appearance quality, feel, resistance to soiling, and ease of cleaning therefore become important.

Odors and safety also matter in indoor environments.
Paint selection needs to consider the environment during use, as well as during application.

Post-Coating Storage and Installation Also Matter for Building Materials

Storage and installation after coating are easily overlooked when coating building materials.

Even correctly coated products can develop problems if handled poorly afterward.

Examples include the following.

• Exposure to rain during outdoor storage
• Moisture trapped between stacked components
• Coating damage during transport
• Cut edges left unrepaired after cutting on site
• Drilled holes used without repair
• Contact with moisture from concrete foundations
• Salt exposure in coastal areas
• Condensation inside packaging

These problems do not arise within the coating process.
However, they may ultimately be regarded as coating defects.

Coating building materials requires checking post-shipment storage, transport, installation, and service environment, as well as factory coating conditions.

Building-Material Coating Risks Requiring Particular Attention in Vietnam

In Vietnam, the following risks are greater for building-material coating.

• High temperature and humidity
• The rainy season
• Outdoor storage
• Salt damage in coastal areas
• Inadequate moisture management on construction sites
• Damage during transport
• Dust
• Insufficient concrete curing
• Inadequate wood moisture content control
• Insufficient repair of edges and cut areas

Outdoor storage during the rainy season is a particularly significant risk.

Leaving coated products outdoors may allow rainwater to enter and remain between overlapping components.
Prolonged exposure in this condition leads to rust, blistering, discoloration, and poor adhesion.

Coastal areas are also more susceptible to salt exposure.
In areas such as Da Nang, Hai Phong, and port areas around Ho Chi Minh City, corrosion protection specifications for outdoor metal components require careful consideration.

Building-material coating specifications in Vietnam need to be based on climate and installation conditions.

The 4M Perspectives CoatureVietnam Should Check

When improving building-material coating, CoatureVietnam checks from the 4M perspectives.

Material: materials

• Whether the substrate is metal, wood, concrete, aluminum, or galvanized material
• Is it for indoor or outdoor use?
• Whether corrosion protection is needed
• Whether weather resistance is needed
• Whether water and moisture resistance are needed
• Whether abrasion resistance is needed
• Whether a wood sealer is needed
• Whether the concrete primer is appropriate
• Whether edge repair materials or on-site repair materials are needed

Method: methods

• Whether pretreatment conditions match the substrate
• Whether wood moisture content is checked
• Whether concrete curing time is sufficient
• Whether film thickness matches the application
• Whether edges, cut areas, and drilled holes are repaired
• Whether the storage method after coating is defined
• Whether repair criteria after on-site installation are available

Machine: equipment

• Whether large or long components can be handled
• Whether curing oven capacity and curing space are sufficient
• Whether baking conditions are stable in powder coating
• Whether pretreatment equipment matches the substrate
• Whether a film thickness gauge is available
• Whether space is available to avoid outdoor storage
• Whether fixtures or packaging prevent damage during transport

Man: people

• Whether operators understand the precautions for each substrate
• Whether they understand the differences between wood and metal
• Whether they understand concrete moisture and alkalinity
• Whether they understand the importance of edge repair
• Whether they understand the risks of storage exposed to rain
• Whether managers share post-installation service conditions with the shop floor

From the Management perspective, specifications, storage rules, installation rules, repair criteria, customer requirements, and warranty conditions need to be clarified.

Questions to Ask During Customer Visits

For building-material coating projects, sales and technical personnel can usefully ask the following questions.

• What is the substrate?
• Is it for indoor or outdoor use?
• Will it be exposed to rain or ultraviolet radiation?
• Will it be used in a coastal area?
• Is it flooring, wall material, a structural component, or furniture material?
• For metal, are edges and cut areas repaired?
• For wood, is moisture content controlled?
• For concrete, are curing time and moisture conditions checked?
• After coating, is storage indoors or outdoors?
• Is damage possible during transport or installation?
• Is cutting or drilling performed on the construction site?
• Have there been complaints about rust, blistering, peeling, or chalking after coating?

These questions identify risks that paint selection alone does not reveal.

Summary: Work Back from the Material and Environment When Coating Building Materials

When coating building materials, first check the substrate and service environment.

For metal, corrosion protection and edge treatment are important.
For wood, moisture content and absorption are important.
For concrete and mortar, moisture and alkalinity are important.
For flooring, abrasion resistance and safety are important.
For outdoor building materials, weather resistance and waterproofing are important.
For indoor building materials, decorative appearance, stain resistance, and ease of cleaning are important.

Post-coating storage, transport, installation, and service environment also affect building-material quality.

Preventing coating problems requires considering the substrate, pretreatment, film thickness, drying, storage, installation, and repair, as well as the paint.

CoatureVietnam regards building-material coating as a process for designing quality to match the substrate and service environment, rather than simply a surface finish.

Coating the Future with Science and Care

In practice, it supports coating improvements suited to Vietnam’s climate, installation conditions, and substrate characteristics.