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Tank Protection and Chemistry

Coatings for Tank Protection and Chemical Industry

Even the everyday environmental influences such as wind, rain and atmospheric gases have an aggressive effect on steel. Unprotected steel corrodes so massively due to the chemical, electrochemical and mechanical influences of the environment that the material can lose essential functions within a few months: statics, protection and tightness are then no longer guaranteed. Particularly high demands are placed on corrosion protection in all areas of the chemical industry and in plant construction. Pipes, pipe bridges, columns and tanks are sometimes exposed to extreme stresses and must still be able to maintain their function permanently and safely – in the worst case, there might be threat of pitting and accidents.

In addition to the general weather influences, a chemically contaminated atmosphere and condensed water often affect the outdoor area of chemical plants. Inside containers or pipes, a variety of sometimes challenging bulk materials can attack the steel. Flammable liquids, fats and oils, aggressive chemicals, acids and alkalis, industrial or municipal waste water, agricultural substrates or even food – they all have a decisive influence on the service life of the container if in direct contact with the inside. This is a challenge for the corrosion protection coating.

Specialised Coating Systems

In order to ensure that all components can withstand such conditions in the long term, special coating systems have been developed that exactly match the respective requirements profiles. In addition, the internal coating of silos, vats, containers or pipes must be well planned and prepared. The expected mechanical, thermal and chemical stress as well as the requirements for safety, occupational health and safety or the service life are often defined in extensive company standards and specifications of the operating companies. Of course, this is primarily about the lasting chemical resistance of the coating to the medium – but in both directions: The product must not attack the coating and the coating must not affect the product and thus limit its suitability for use.

This point is particularly important for potable water or food. In order to withstand the stress over long periods of time, the inner coating selected must be firmly bonded to the container wall or pipe. In addition to having very good adhesive strength, it should be shock and impact-resistant. A lot depends on accurate processing and application of the coating: Its layer thickness must not be less than the specified minimum at any point and it must be applied pore-free.

Good Surface Preparation Counts

EN 14879-1 provides a demanding framework. It regulates the principles for the coating of industrial plants to protect them against aggressive media. The structure of the inner surfaces and the surface preparation play an important role here. Corrosion-prone and hard-to-coat areas should be excluded from the outset. For example, cracks must be avoided at all costs and burrs or edges must be rounded off. Slag enclosed in the welded material or weld defects are prohibited, as are greasy, oily residues or rust. In addition, it is recommended to blast the surface (with corundum) and to achieve a roughness depth of at least 50 μm so that the coating can enter into a sufficiently firm bond with the substrate.

Standards are also specified for the application of the coating materials, for example, whether a complete coating of all interior surfaces, from the floor to the roof, is necessary (for example, for the storage of aviation fuels) – or whether a partial coating of the floor and the adjacent wall areas is sufficient. In addition, there may be different zones in a container, which must be provided with different layer thicknesses, for example, because substances with certain properties can accumulate in the soil area.

The choice of application technology is also by no means arbitrary. For example, an airless application is particularly suitable when low equipment use and manual preparatory work are required. Hot spray applications, on the other hand, harden quickly and are particularly suitable for large areas.

Tested Standards

In the areas of tank protection, chemical industry and plant construction, it is often about substances that are hazardous to health or water. High requirements must be met in order to ensure that they do not enter the environment uncontrollably. For example, the internal coating of containers and pipes in stationary plants must be generally approved by building authorities. The German Institute of Building Technology (DIBt) issues these approvals in accordance with the "Approval Principles for Coating Materials for the Production of Internal Coatings of Steel Containers for the Storage of Water-polluting Liquids". For successful approval, chemical resistance is regularly proven by an independent testing body. In order to ensure the standards in processing, the specialist coating company also needs a qualification certificate according to WHG (Federal Water Act) or AwSV (Ordinance on Facilities Handling Substances that are Hazardous to Water).

Due to the variety of different media, their concentration and their chemical properties, there is no alternative to tailor-made system solutions. It is therefore helpful to consult resistance lists at an early stage. These provide information about the resistance of coating systems to numerous media – long-term tested both in direct contact with the medium and in the vapour zone. However, responsible management of the storage or transport of such media includes not just the optimised selection of the respective coating system. Only industry-oriented advice and expert service lead to the desired quality and safety.

Internal Linings for Tanks, Vessels and Pipelines

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Long time proved and tested systems

Typical Application Areas
Interior Tanklinings
Exterior Tank Coatings
Plants Subject to Atmospheric Corrosion
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