Metal is one of the most difficult surfaces to coat because it has a low surface energy that discourages the adhesion of coatings and paint to it. Adhesion failure to the metal substrate is the primary reason for corrosion of metal substrates in extreme climate conditions. In a similar way, adhesion failure of a topcoat to the primer is the root cause of premature failure of topcoats in adverse climates.
To provide guidance to architects, engineers, specifiers, applicators and other parties in the application of coatings to metal, ISO 12944 is the internationally recognized industry standard for corrosion protection. It helps in the proper selection of coatings for different environmental exposures. ISO12944 covers nine parts with key components of the standard addressing environment classification, protective paint systems, laboratory test methods and more.
ISO 12944 includes corrosion categories, including five environmental categories for onshore assets that range from C1 (very low corrosivity) to C5 (very high corrosivity environments) and CX (offshore environments) and immersion categories (IM1-IM4). This standard is intended to assist the user in the best practice for protecting steel surfaces from corrosion and to select the right coating system based on the environment and required durability.
Finding the correct ISO 12944 corrosion protection involves three higher level steps:
- Defining the corrosion category that matches the project’s environment.
- Determining ISO durability requirement, with the main factors influencing durability choice including atmospheric conditions, structure design, accessibility of asset and application conditions.
- Selecting the system based on project requirements.
The overwhelming majority of protective coatings used today are solvent-based coatings, however new advances in water-borne technology are giving users more environmentally friendly options with similar performance, and in some cases better performance in many kinds of environments. Water-borne, self-crosslinking polyurethane dispersions (PUDs) offer excellent adhesion to metal surfaces and outstanding topcoat properties. The result is a single/multi-coat solution for a variety of protective and industrial applications, as well as ISO 12944 applications.
Aptalon™ Polyamide PUDs
Aptalon™ Polyamide Polyurethane Dispersions from Lubrizol bring a new range of performance to coatings, specifically for water-borne technologies. The technology offers a new platform for resin development that uses patented polyamide polyol technology to deliver hardness, adhesion, hydrolysis resistance and abrasion resistance that far exceed other direct-to-metal (DTM) water-borne systems, as well as a topcoat on primers. Aptalon™ M8100 and Aptalon™ M8120 can be used for many environmental conditions, including in ISO12944 protective environments (C1-C4) end-use metal applications (OEM factory and field applied).
These water-borne, self-crosslinking PUDs provide hydrolysis and chemical resistance for excellent protective properties. Water-borne PUDs using Aptalon technology will meet performance properties of many 2K solvent-borne finishes without the need for external cross-linkers. And, Lubrizol PUDs are NMP, NEP, and APEO-free to allow for globally compliant formulations.
Typical applications of PUD-based paint and coatings for DTM and topcoats for medium duty applications include interior/exterior industrial, automotive, agriculture and construction equipment, building construction, and transportation component markets where metal surfaces can be exposed to environmental conditions – as well as being used in ISO 12944 protective environments.
Lubrizol has extensive experience helping coating formulators ensure the properties/performance they are trying to improve using PUDs. Visit Protective Coatings for additional information or contact a Lubrizol expert to learn more about our polyurethane dispersions for various protective coating environments – including ISO 12944 protective environments.