Metal Coatings: The complete guide for industrial applications

Table of Contents

What are metal coatings?

What are metal coatings?

Metal coatings refer to paint that is applied to metal to protect surfaces and prevent corrosion in order to increase the product’s lifespan.

In short: Every paint is a type of coating, but every coating is not a paint. Coating can consist of many layers of paint, and refers to the end result that remains once the work is finished. 

There are multiple types of metal coatings, including simpler metal coatings and metal surface treatments, as well as more corrosion-resistant metal coatings. 

To fully get a grasp on the different types of coatings, let’s go a bit deeper into the chemical components that make up industrial paints for metal. The most important component is the resin; and that could be epoxy, alkyd, acrylic, polyurethane, and more. 

Next is the solvent, which is what essentially transforms the paint into a liquid. In the process, all the pigments and other raw materials are dispersed or mixed in water to form an even liquid. This component can be a chemical solvent or water. Due to this, coatings can be categorized as either solvent-borne or water-borne depending on the solvent used. Other components that are used in a paint formula are pigments, fillers, thickeners, and other additives. 

At Tikkurila, our product range for metal surfaces varies from traditional alkyd paints to modern high-tech direct-to-metal (DTM) polyurethanes. These include solvent-borne primers and topcoats, more environmentally sound high-solids paints, solvent-free coatings and sophisticated water-borne products.

What are the purposes of metal coatings?

Rymas Herman, Business & Portfolio Development Director, discusses the main purposes of metal coatings.

Different types of metal coatings are naturally recommended for different types of purposes and industries. Let’s go through some of the most common purposes for metal coatings.

 

Metal coatings purposes

 

Corrosion protection

The main purpose of all types of metal coatings is simply to protect metal products from natural occurrences such as corrosion. 

Both water-borne and solvent-borne coatings work well in industrial use, but different types of coatings have different pros and cons. This means that before deciding on which coating to go with, you should always consider specific products and the specific use case at hand. 

There are many different metal coating methods for corrosion prevention, and due to their various features and qualities, each type performs differently and according to different parameters.

 

Better durability

In addition to protection from corrosion and natural elements, using quality metal coatings ensures better durability for the entire metal structure. 

Coatings that last longer also directly result in longer maintenance painting intervals, which in turn helps you manage costs in the long run.

 

Improved appearance

Metal coatings result in the long-term preservation of a structure’s cosmetic appearance, even under extreme conditions. With suitable and proper metal coatings, you can create a long-lasting finished surface with your preferred aesthetics including paint colour, gloss level, and more.

 

Increased chemical and water resistance

Applying a proper metal coating means forming a tough surface on your structure, and, in addition to protection from corrosion, the coatings are also highly resistant to any abrasion or chemical stress. 

If you need a metal coating for an environment of high humidity, it’s a good idea to consider solvent-borne coatings. To find out more about their differences and which ones you should consider for your structure, you can read our article on the differences of water-borne and solvent-borne coatings.

 

Fire protection

Certain metal coatings can also be used to protect the substrate from the effects of fire. Having a metal coating that protects from fire helps by giving additional time before the steel reaches a temperature at which it loses its load bearing capacity. This extra time allows evacuation of the building and a chance for the emergency services to control the fire. 

For example, one of our products — the Fontefire ST 60 — is a water-borne one-component intumescent coating that provides you with a heat expansion binding reaction that results in the creation of an insulating foam layer, which then protects your metal structure from reaching critical temperature for a certain period of time.

 

Additional functions

Some metal coatings serve other specific functions, such as preventing condensation. Our GrafoTherm line, for example, is a one-component water-borne anti-condensation coating for steel roofing sheets, steel structures and other metal surfaces, where condensation and dripping-water problems occur.

How are metal coatings used?

Our wide range of different painting systems for metal can be used for any metal surface, whether interior or exterior, and we offer ready-made solutions for selected industrial segments.

All of our different coating and surface treatment systems for metals have different use cases. For instance, maybe you need metal coatings for a harbour environment, where your structures are frequently subjected to harsh working conditions and corrosive climate stress. In these types of conditions, machinery and equipment require a higher level of protection than the same machinery used indoors.

Durable coating for Jännevirta bridge

Durable coating for Jännevirta bridge

To replace Finland’s sixth largest bridge at the end of its lifetime, it took 2,430 tons of pre-coated steel structures. Ruukki Construction supplied and installed the structures, and we pre-painted them at our factory.

Jännevirta bridge in numbers

577 metres long and 15 metres wide
20–30 metres length in each steel section
25 metres above water at highest point
2,430 tons of steel structures
15,000 litres of paint were used

Read the full story

As another example, you might need high-performance, environmentally compliant solutions for the agricultural, construction, and earth-moving machinery and equipment (ACE) market. Our high-performance systems include water- and solvent-borne solutions that provide better protection while using fewer coats of paint.

Our solutions for different types of steel structures include coatings that protect against mild stress for interior surfaces, heavy stress for exterior surfaces, or even extreme chemical stress. We also offer a wide color range, including metallic colors that can also provide an aesthetic dimension.

Taking a Ferris wheel project to new heights

Taking a Ferris wheel project to new heights

In a partnership project with Karusel PC LLC., we painted six amusement park ridesincluding Ferris wheelswhere safety, reliability, and durability are extremely important. 

For one Ferris wheel, we:

Painted more than 3,000 m3 of metal surfaces (not including the cabins)
Selected paint and lacquer systems that took climate pattern for the specific city where the ride was to be installed into account
Ensured the paint shop workers mastered the painting techniques for Ferris wheels from scratch

 

Read the full story

There are many paint systems for maintenance and touch-up painting that are easy to use and do not need blast cleaning surface preparation. We also offer a system for surfaces immersed in water. 

If you are not sure what kind of painting system or coating and surface treatment system you need for your specific metal structure, please feel free to contact us to find out more about your options.

Different types of coatings for metal

As mentioned above, different types of metal coating products range from traditional alkyd paints to modern high-tech DTM polyurethanes including solvent-borne primers and topcoats, more environmentally sound high-solids paints, solvent-free coatings, and also sophisticated water-borne products. 

Next, let’s do an overview of the different categories of metal coatings.

Traditional products

Our traditional products for metal surfaces ensure cost-effective and long-term protection against corrosion and wear. 

All of our metal coatings and systems have been tested both in laboratory and in real-life conditions, and the majority of Tikkurila products have been officially approved in many countries.

Our traditional products include a variety of alkyd and epoxy primers and topcoats, as well as polyurethane and acrylic paints, and zinc-rich primers.

High-solids products

Our high-solids products for metal surfaces have a very low VOC content, which helps decrease harmful solvent emissions.

Some of our high-solids products and metal coatings can also be used as a DTM system, which in turn helps you reduce production costs. 

High-solids metal coatings that Tikkurila offers include a variety of alkyd and epoxy topcoats, as well as epoxy mastics, polyurethane paints, and oxirane esters.

Water-borne products

The technical properties and performance of our water-borne coatings compare favourably with those of solvent-borne paints. They fully comply with exacting industrial quality standards and the latest environmental regulations.

Similarly to our high-solids products, some of our water-borne coatings can be used as a DTM system, reducing production costs. We offer many different water-borne lacquers, primers, and topcoats. 

There are, however, still many misconceptions circulating about water-borne products. You can read our article on the differences of water-borne and solvent-borne metal coatings, and our other article on the truth behind 6 common water-borne metal coatings misconceptions to find out more.

Picking the right types of metal coatings

Minna Perttu from Research, Development, and Innovation at Tikkurila shares how to pick the right types of metal coatings for your business.

As there are many different types of metal coatings, there are naturally multiple different factors to consider when choosing the right coating product for your specific needs. 

Your goals

To make the right choice, take the time to consider your goals with metal coatings. Ask yourself the following questions before making a decision: 

What kind of painting conditions are we working with?
What kind of environment is our end product used in? (Is it indoors? Or are there harsh weather conditions?)
How long do we want the paint to hold? With some products, such as mining equipment, the paint is not expected to stay on the surface for longer than for the product’s first use. 
What is our company’s mindset towards sustainability? You might choose to use water-borne coatings, for example, if your company’s long-term goal is to reduce your VOC emissions and the negative impact your operations have on the environment. 
What demands are we currently facing
Which painting system standards do we have to comply with?


Your processes

Consider the following questions about your current ways of working:

What paints and coatings for metal surfaces are we using today? 
What types of metal surfaces are we working with? 
What equipment are we currently using? 
Do we paint first and then assemble, or is it or other way around?  


The project timeline and deadline

Ask yourself the following questions when considering your project timeline:

What drying time do we need?
When are we able to pack the dried product? 
How much should we be able to paint in one day?


Your budget and costs

Finally, consider your budget. Remember that some products require a higher initial investment, but pay off in the long term. For example, water-borne products are priced a bit higher because the raw materials to develop these products are priced higher. But after the initial investment of adjusting our equipment and processes, you start gaining back your investment. In fact, you can reduce your overall operations cost by using water-borne products. You don’t need to invest in explosion-proof equipment, highly flammable paint insurance, or specially trained personnel to transport the products because water-borne products aren’t flammable. Plus, wet water-borne paint can be cleaned with water, meaning you’ll save expenses by not using as many cleaning supplies. 

Additionally, using  DTM products rather than primers and topcoats will help reduce process time since only one application is needed. 

Remember that the cost of paint is just one part of the total project cost. The true cost of painting an object or unit takes into account all aspects of the treatment. And depending on what paint products you use, the total cost can be reduced by less dry film thickness (DFT), and shorter process time (application, drying). 

Use our cost calculator for metal products to better plan your budget.
Metal coatings standards

Metal coatings standards: What you should know

As with any field or industry, there are certain standards and regulations that need to be taken into account when deciding which product to go with. 

With metal coatings, all the materials and systems you use need to fulfill either international standards like ISO 12944, which is a global corrosion protection standard, or any internal standards your individual customer may have. 

This means, in short, that all systems need to be properly tested to these standards. 

The materials and systems we at Tikkurila supply comply with ISO 12944. Part 5 of this standard defines protective coating systems for different corrosive environments: C2, C3, C4, C5. The standard also determines durability ranges, which affects the time to the first major maintenance round: L, M, H and VH.

Tikkurila also has paint systems approved according to other standards as well. These include Norsok (Norway), Silko (Finland), GOST (Russia), and so forth. 

Part 5 of ISO 12944 defines protective coating systems for different corrosive environments: C2, C3, C4, and C5, and it also defines systems according to their ISO 12944 corrosion class. 

The standard also determines durability ranges, which affects the time to the first major maintenance round: L, M, H, and VH.

Working with metal coatings

Žydrūnas Čepkauskas, Group Portfolio Development Manager at Tikkurila, shares expert tips for working with metal coatings.

Next, let’s go through a couple of useful expert tips for working with metal coatings—from surface preparation to maintenance.

 

Metal coating equipment

 

Metal coating equipment 

For different types of coatings, different equipment is required in order to allow the product to work its magic. 

For example, solvent-borne metal coatings require special explosion-proof equipment, as the products are highly flammable. In turn,  water-borne products aren’t flammable and don’t require such equipment. On the other hand, water-borne products still require equipment with stainless steel in all parts that are in contact with the wet water-borne paint.

Surface preparation

The success of your metal surface treatment largely depends on the surface to which it’s applied. Before applying the coating on your metal surface, the surface needs to be properly cleaned and roughened to ensure adhesion. The right level of cleanliness will help ensure the right performance of the coating. 

For instance, solvent-borne coatings are more forgiving of contaminated surfaces, while water-borne coatings always require a clean environment and surface—so, depending on which type of coating you are going with, ensure that the level of cleanliness is up to par with what the product requires. 

You can follow this example of a water-borne product’s recommended surface cleaning:

Steel surfaces: Degrease and blast clean to grade Sa2½. (ISO 8501-1) If blast cleaning is not possible, phosphating is recommended for cold rolled steel to improve adhesion. 

Primed surfaces: Oil, grease, salt, and dirt are removed from the surface by appropriate means. Repair any damage to the primer coat. Check your product's PDS for guidance regarding previously primed surfaces. 

 

Application

Your application methods could depend on several factors such as your equipment, the type of paint you’re using, production speed, output speed, and whether you’re applying on-site (at the painting shop) or off-site. 

Depending on these factors, you might use application robots, automatic painting lines, and different spraying techniques such as conventional, Airless, Airspray, and electrostatic spraying. For off-site maintenance and touch-ups, you might also use brush and roller application. No matter which method you use, correct paint application is key to get a long-lasting finish with metal coatings. 

Drying

If you are painting in very humid conditions, you might need to pay extra attention to drying. 

Especially with water-borne coatings, the water in the paint can’t evaporate properly in extremely humid conditions, and thus the paint will take longer to dry.

A possible solution for this is to apply metal coatings in a room where you can control the climate and keep the humidity at a certain percentage. The recommended humidity level is 20-70%.

In many cases you may fasten the drying time by increasing the temperature. The recommended temperatures depend on the paint. 

Maintenance 

The correct surface preparation and paint application will improve the coating’s performance lifetime, but some maintenance will most likely be needed after a period of time when working with metal coatings. 

There’s a wide selection of repair and maintenance products for industrial metal surfaces to choose from, and we at Tikkurila are of course available to answer any questions you may have

Chemical resistance

You might need metal coatings that require specific chemical resistance, such as oils, fuels, acids, and chemical solvents, among others. When considering metal coatings for a particular chemical environment, consider the following factors:

Chemical exposure
Operating temperature
Mechanical abrasion
Degree of protection required (immersion or splash/continuous or limited)
Metal coatings conclusion

Conclusion

To sum up everything we’ve gone through, there are multiple types of metal coatings, including simpler metal coatings and metal surface treatments, as well as high-tech protective metal coatings—all of which are designed for different purposes. 

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Further reading

FAQ – Metal surface treatment

While the main purpose of all metal coatings is to protect against corrosion, each type of product performs differently according to different parameters. You want to choose the right metal coatings products for your specific business needs without compromising on quality and durability.

The truth behind 6 common water-borne metal coatings misconceptions

Do industrial water-borne coatings perform as well as solvent-borne coatings? Can water-borne coatings really protect metal surfaces from corrosion? Won’t it require too much effort and investment to switch to water-borne solutions?