Industrial tank coatings: when are they necessary, when are they unnecessary, and which coating systems should be considered?

Depending on their application, industrial tanks must meet different technical requirements and regulatory standards. In many cases, these can be fulfilled economically and durably not only through the right material selection, but also through purpose-designed tank coating systems, whether internal or external. Based on more than 10 years of experience in tank manufacturing, we have put together an overview of when coating is worth applying, when it is unnecessary, and which factors should guide the selection of the right coating system.

Tank coatings and surface treatment: what is the difference?

Both processes are used to improve the properties of a tank surface, but it is important to distinguish between tank coatings and surface treatment.

Industrial tank coatings are protective layers applied to the surface of the tank, such as epoxy, polyurethane, vinyl ester, rubber lining or fluoropolymer lining, typically for corrosion protection or chemical resistance.

Surface treatment, by contrast, does not involve applying a separate layer. It refers to the preparation and refinement of the tank’s own surface, such as grinding, polishing, pickling and passivation, primarily to improve hygiene and cleanability.

The role of industrial tank coatings

The purpose of a coating is to ensure that the surface properties of the tank meet the requirements of the stored medium and the relevant regulations. These may include:

• corrosion protection and chemical resistance,
• hygiene, cleanability and surface roughness control to reduce the risk of contamination build-up,
• abrasion and impact resistance,
• resistance to thermal and chemical stress.

In addition, coatings can also offer economic benefits, such as a lower total cost of ownership (TCO), fewer failures, less repair work and easier cleaning.

When is coating justified?

Tank coatings are justified in the following cases:

• Increased exposure: when the aggressiveness of the medium or extreme operating conditions mean that the base material alone is not sufficient and an additional protective layer is required.
• An exceptionally smooth, easy-to-sterilise surface: where required to comply with specific standards and regulatory requirements.
• Economic considerations: when a lower-cost base material combined with the right coating system provides the best total cost of ownership over the full service life.

When is tank coating unnecessary?

Tank coating is unnecessary when the properties of the base material already meet the relevant requirements. Typical examples include the following:

• The stored medium is not corrosive. If the medium stored in the tank does not attack the tank material, coating is not required. Examples include storing compressed dry air, dry inert gases or mineral oil in a carbon steel tank.
• The tank material is inherently corrosion-resistant. If the tank is made of stainless steel, aluminium or another corrosion-resistant alloy, coating is generally unnecessary. For example, stainless steel tanks used for acidic or alkaline media.
• The environmental conditions do not promote corrosion. If the tank is enclosed, dry, and not exposed to moisture or condensation, the risk of corrosion is low. For example, an indoor tank operating in a dry environment.
• The tank is intended for temporary use only. In short-term or trial-use applications, corrosion may not become a relevant issue during the planned service period.
• The coating would react with the stored material. If the coating material could adversely affect the stored substance, for example through dissolution or contamination, it is better to avoid coating and select a more suitable resistant material instead.

Tank coating types

In tank manufacturing, different specialised coating systems are used depending on the medium involved, the operating temperature, the expected mechanical loads, and the applicable hygiene requirements.

Epoxy

Epoxy coatings adhere very well to steel and provide good corrosion protection, chemical resistance, as well as water and oil resistance. They are typically used for drinking water tanks, wastewater tanks, and chemical or fuel storage tanks, and can also be applied in thicker layers where required.

Polyurethane (PU)

Polyurethane is a flexible coating with good impact resistance, abrasion resistance, and UV resistance. It is most commonly used on the external surfaces of outdoor tanks and as a topcoat for weather protection.

Vinyl ester (and polyester) resin

These systems are a good choice for strongly acidic or alkaline media and for higher operating temperatures. They cure quickly and can be reinforced with glass fibre. Typical applications include the chemical industry, such as acid storage tanks, galvanising plants, and reactors. Polyester is generally used for more general-purpose applications, while vinyl ester is specifically recommended for aggressive chemicals and higher temperatures.

Rubber linings and elastomer systems

These provide a thick, flexible protective layer with good impact and abrasion resistance, while also absorbing vibration and thermal movement. They are typically used for abrasive media such as sludge or sand, and in mining, cement industry, and power plant applications.

Special coatings – oil-resistant systems

These are coatings developed for specific performance requirements, such as resistance to oil, fuel, or certain chemicals, where general-purpose systems do not provide a sufficient level of protection.

Fluoropolymer linings – PTFE, PFA, FEP

These linings offer outstanding chemical compatibility and a non-stick surface, and remain stable even at elevated temperatures, although they are relatively costly. They are typically used for highly aggressive acids or solvents, and in pharmaceutical and chemical industry reactors and mixing tanks.

Zinc-based and galvanising systems – cathodic protection

For steel surfaces, these systems provide electrochemical corrosion protection in the form of a primer or protective layer, mainly in outdoor applications and strongly corrosive atmospheres. They are commonly used on outdoor tanks, pipelines, and in coastal or marine environments.

How to choose the right coating system

The answer always depends on which property of the selected tank material needs to be improved. These requirements may vary depending on the application. We have summarised the most important considerations in the table below.

The role of coatings across different industries

Industry examples – practical recommendations for different applications

Based on our experience in tank manufacturing, we have collected a few practical recommendations on which coating systems are worth considering in different industries.

Wine industry tanks

These tanks are typically made of stainless steel (AISI 304/316 or higher grade), so internal coating is not required. In outdoor installations, however, it is worth considering an external polyurethane coating to protect the tank against weather exposure, significant temperature fluctuations, and UV radiation.

Coating a carbon steel tank by painting

Chemical industry tanks

In chemical industry applications, material selection is determined by the aggressiveness of the stored medium. We manufacture chemical tanks from both stainless or acid-resistant steel (316L/316Ti) and carbon steel. As carbon steel is not corrosion-resistant, it always requires appropriate protection.

The structure of the coating system depends on the external and internal exposure conditions:

• External protection: In industrial environments, simple painting is not sufficient. For long-term protection, we apply multi-layer systems designed in accordance with the corrosion category defined by ISO 12944 (C3, C4, C5), for example an epoxy primer, an intermediate coat and a UV-resistant polyurethane topcoat, to ensure resistance to weathering and industrial atmosphere.
• Internal protection: On the internal surface, the key factor is the chemical aggressiveness of the stored medium. In such cases, we do not use conventional paint, but a special chemically resistant lining or a multi-layer solvent-free epoxy system. The tank designer always determines the required number of coating layers based on the applicable requirements and specifications.

Tanks used in battery manufacturing

In the manufacture of electrolyte storage tanks for battery production, the service conditions are more demanding, which can be addressed by using special coating systems applied in two or three layers. Vinyl ester resin coating can also be a suitable solution.

Tanks for storing highly corrosive substances

For tanks intended to store acids, alkalis or other highly corrosive substances, vinyl ester and fluoropolymer linings such as PTFE, FEP or PFA are suitable options. These are typically used in the pharmaceutical industry and in fine chemical manufacturing.

Food industry, agricultural and water treatment tanks

For all three fields, stainless steel tanks are generally the most suitable option in terms of technical and regulatory requirements. As a rule, these tanks do not require coating. Where regulations call for an exceptionally smooth surface, a food-grade epoxy coating may be applied.

Carbon steel tank with internal and external coating

Process discipline and quality control are critical in tank coating

It is not enough to select the right base material and coating system. Professional application and proper quality control are just as essential. The main steps are as follows:

1. Surface preparation: for example by abrasive blasting.
2. Application of coating layers: for painted tanks, this typically includes primer, intermediate coat and topcoat, depending on the material and specification.
3. Coating inspection: after production, we carry out coating thickness measurements, with the results documented in an inspection report.
4. Maintenance: if the coating shows signs of wear, we inspect the tank on site and make recommendations for repair.

Custom industrial tanks that meet every requirement – from Duna Steel Tech

For our clients, we always manufacture the tank solution that best fits their requirements, including a suitable coating system where needed. Whether you approach us with detailed plans or only an initial concept, our engineering team will help you find the most effective and most economical solution. If you have any questions, please feel free to contact us.