Types of industrial coatings: a selection guide by environment

There is no single best industrial coating: epoxy protects most surfaces in atmosphere and immersion, novolacs and vinyl esters handle severe chemical service, polyurethane and polysiloxane serve as UV-resistant topcoats, zinc and metallizing protect steel galvanically, intumescent coatings address fire, and rubber and ceramic resist abrasion. The service environment, the achievable preparation and the work window decide.

An industrial coating is a layer, or a system of layers, applied to steel or concrete to protect it from corrosion, chemicals, wear or fire. Each family has a range where it excels and conditions where it fails. This guide helps maintenance managers and project managers in Quebec and Ontario sort through the options before requesting a quote. It complements our reference page on protective coatings.

How are industrial coatings classified?

Industrial coatings are classified by how they protect: barrier, galvanic protection, mechanical resistance or passive fire protection. Looking at them this way avoids comparing products that do not solve the same problem.

• Barrier. Epoxy, vinyl ester, polyurethane, polyurea and polysiloxane isolate the substrate from the environment. Performance depends on thickness, film continuity and adhesion.
• Galvanic protection. Zinc-rich primers and zinc or aluminum metallizing sacrifice themselves in place of the steel at damaged spots.
• Mechanical resistance. Rubber and ceramic-filled coatings absorb or resist abrasion and impact.
• Fire protection. Intumescent coatings swell under heat and delay the temperature rise of structural steel.

Most structures receive a system that combines several families: a primer, one or more intermediate coats and a topcoat. ISO 12944-5 describes these systems for steel in atmosphere and immersion.

Which coating for which environment?

The table below summarizes the generally recognized uses, environments and limits of each family. The manufacturer's data sheet and the project specification remain the reference for a given service.

For steel in atmosphere, our guide to ISO 12944 C3, C4 and C5 paint systems shows how the corrosivity category drives the system.

When to choose epoxy, novolac or vinyl ester?

Standard epoxy is chosen for most primers, intermediate coats and tank interiors in water or moderate chemical service, novolac when temperature or chemical aggressiveness rises, and vinyl ester for strong acids and oxidizers. All three form hard, adherent films, but with different tolerances.

• Epoxy. Good adhesion, good resistance to water and many chemicals. It chalks in sunlight, so outdoors it receives a topcoat.
• Novolac epoxy. Higher crosslink density, hence better chemical and thermal resistance. See the novolac epoxy entry.
• Vinyl ester. Often applied with flake or fibre reinforcement as a thick lining. It calls for strict control of conditions and timing.

For a vessel interior, our article on industrial tank lining selection walks through the approach based on the stored product.

Which topcoats resist UV and weather?

Aliphatic polyurethane and polysiloxane are the common topcoats when the structure is exposed to sun and weather. They hold colour and gloss where epoxy chalks.

Polyurethane is the most widespread topcoat on exterior structures and equipment. It recoats well and is easy to repair during maintenance. Polysiloxane aims for longer retention of appearance and protection, sometimes with fewer coats, but it needs a compatible primer and careful application. In both cases, the topcoat does not make up for an inadequate primer or preparation.

Where does polyurea fit?

Polyurea suits surfaces that need a thick, flexible, fast-curing membrane: containment basins, roofs, abrasion and impact protection. Its fast cure shortens downtime, but it requires high-pressure plural-component equipment and a primer suited to the substrate.

On concrete, polyurea needs a dry, prepared substrate, otherwise it blisters. It is not a universal choice for chemical immersion: compatibility is checked product by product. Our polyurea coatings page presents the applications where it makes sense.

How do zinc and metallizing work?

Zinc and metallizing protect steel galvanically: zinc, more active than steel, corrodes in its place at scratches and holidays. A zinc-rich primer provides that protection under a paint system; metallizing deposits a layer of pure metal or alloy by thermal spray.

Zinc-rich primers are described in SSPC-Paint 20. Metallizing follows ISO 2063 or SSPC-CS 23.00 / AWS C2.23. Both require high-grade blasting and an angular profile. Our comparison of zinc vs aluminum thermal spray helps choose the metal, and our thermal spray metallizing page describes the service.

When is intumescent, rubber or ceramic needed?

These three families answer specific needs: intumescent for fire, rubber and ceramic for wear. They are not general-purpose anticorrosion coatings, even though they fit into a system that also protects against corrosion.

• Intumescent. It protects structural steel to the fire-resistance rating required by code and verified by testing (in Canada, per CAN/ULC-S101). Thickness depends on the section and the target rating. See our intumescent coatings page.
• Rubber. It absorbs particle impact in chutes, slurry lines and some acid vessels. It is installed as bonded sheet or cast, depending on the item. See our rubber lining page.
• Ceramic. Ceramic-filled epoxies and alumina tiles resist sliding abrasion in severe wear zones. They tolerate direct impact less well than rubber.

How to avoid choosing the wrong coating?

You avoid a poor choice by starting from the actual environment, then checking achievable preparation, temperature, application conditions and the shutdown window. The best product fails if it is applied on a poorly prepared surface or outside the intended conditions.

• Describe the environment. Products, concentrations, temperature, abrasion, UV, immersion or splash.
• Check the preparation. A system that needs high-grade blasting does not suit a job where only power tool cleaning is possible. Grades are explained in our NACE 2 / SSPC-SP 10 surface preparation guide.
• Check compatibility. Primer, intermediate and topcoat must be compatible, especially when overcoating an existing coating.
• Set the checks. Thickness per SSPC-PA 2, adhesion per ASTM D4541, holiday testing in immersion.

Our crews and qualified subcontractors work from LaSalle, including Montreal and Abitibi-Témiscamingue. Send photos, dimensions and a description of the environment through the request a quote form: pricing on consultation, reply within 24 business hours.

Frequently asked questions

What is the most widely used industrial coating?

Epoxy, as a primer, intermediate coat or lining. Outdoors, it is almost always topcoated with polyurethane or polysiloxane because it chalks under UV.

Can any topcoat go over an epoxy primer?

No. The topcoat must be compatible with the primer and applied within its recoat window. The data sheet and the system specification state the accepted combinations.

Does a wear-resistant coating also protect against corrosion?

Partly. Rubber and ceramic form a barrier, but their main role is wear. On steel, preparation and sometimes an anticorrosion primer are still needed under the wear layer.

How do I know if my existing coating can be overcoated?

Through a survey: identification of the existing system, adhesion, thickness and surface condition. A compatibility patch test on a small area confirms the choice before full repainting.