Powder coatings are increasingly preferred over conventional solventborne and waterborne coatings. These types of coatings offer a high environmental advantage and, in addition, they are key to the economic benefit in the coating process. One of the reasons is that powder coatings are 100% solid, solvent-free materials that process with close to 100% utility. Even more important is their high technical performance.
Corrosion ProtectionAs the global market leader, DSM Powder Coating Resins specializes in the innovation, development and manufacture of polyester resins for powder coatings. Corrosion-protective powder coatings, based on environmentally friendly polyester, are a new DSM development in line with the company strategy on sustainability. Coatings are the primary solution to prevent corrosion of metal, and steel is the most commonly used metal. Depending on the environment where the product is in use, it needs protection from corrosion.
Uralac® CorresUralac® Corres is especially developed for corrosion protection on steel and can be used in many market segments. The main target segments range from thin, flat steel applications like metal furniture, shelving, heating/ventilation and domestic appliances to equipment, automotive parts and even heavy steel applications like ACE and construction beams. Corrosion protection is needed for every single application; depending on the expected lifetime and conditions of use it has its own specified requirements.
Direct Comparison StudyTo support and prove the above claims, DSM ran a direct comparison with common powder coating systems. Uralac® P 7604 Corres was applied on R 46 Q-panels and compared after a 480 h natural salt spray test according to ISO 9227 with standard references like a pure epoxy, a 70/30 hybrid and a 95/ Primid system. Figure 2 clearly shows the good performance of Uralac® Corres P 7604 Corres against all three references.
In addition to passing the industry requirements, DSM used analytical tools to support its theory on the enhanced barrier properties.
Resistance MonitoringTo support the practical results on salt spray, the Dutch research and test institute TNO Science & Industry Den Helder monitored the resistance against corrosion with Electrochemical Impedance Spectroscopy (EIS). The EIS technique determines the anti-corrosive properties of a coating. This is done by measuring the resistance to an alternating current in an electrochemical cell system. The higher the measured coating resistance, the better the anti-corrosion performance.
Figure 3 shows that the anti-corrosive performance of Uralac® Corres remains good before and after the natural salt spray test, and is better than the tested reference systems. The high resistance values, also in comparison with TNO industry classification, support the theory on the high barrier against corrosion of the Uralac® Corres polyester. Due to the exceptionally good corrosion protection in metal coating, the Uralac® Corres technology offers the possibility to significantly reduce and sometimes completely eliminate chemical pre-treatment steps.
Figure 4 illustrates the reduction in process steps for a nine-stage iron phosphate pretreatment process compared to a simple cleaning process needed for Uralac® Corres.
In addition to the good technical performance, Uralac® Corres can save production space and reduce new investments especially for new lines.
Environmental ImpactBecause Uralac® Corres significantly reduces or completely eliminates pretreatment steps it removes the usage of environmentally hazardous chemicals. Uralac® Corres fulfills all requirements up to 480 h NSS without any pretreatment. This is a 100% saving on hazardous phosphate chemicals, a significant risk reduction in handling and waste disposal related to the phosphate chemicals. It translates to a better work environment.
ConclusionWith high-performance corrosion protection and an ability to eliminate pretreatment steps and replace epoxy-based primers in the coating process, DSM Uralac® Corres opens a new window of opportunity for corrosion-protective coatings. DSM Powder Coating Resins continues to contribute with its cutting-edge innovation to the development of the coating industry.
For more information about the current and future portfolio of DSM Powder Coating Resins, visit www.dsmpowdercoatingresins.com, or contact your local account manager.
This article was first published in PPCJ, October 2008.