In recent years, the global market for hot-dip galvanized steel has experienced significant growth, reaching a remarkable $86.7 billion in 2020 with an annual growth rate of 2.3%. Around 75% of the demand is driven by the construction and automotive markets.
Hot-dip galvanized steel, known for its zinc-coated surface achieved through a hot dipping process, is highly sought after for its exceptional durability, strength, formability, and corrosion resistance.
Paint adhesion on HDG (Hot-Dip Galvanized) steel parts is a critical aspect of ensuring the longevity and performance of coated metal components across various industries. The bond between the paint and the substrate not only enhances aesthetics but also provides essential protection against corrosion and environmental factors.
What is paint adhesion and why is it important?
Paint adhesion refers to the ability of a coating to firmly bond to the surface of a substrate, forming a durable and protective barrier against corrosion, weathering, and other environmental factors. In the context of steel structures, paint adhesion plays a critical role in safeguarding against rust, maintaining aesthetics, and prolonging the service life of the material.
Hot-dip galvanization is a widely employed metal treatment method for steel, wherein the surface is coated with a layer of zinc to provide corrosion protection. However, for optimal performance, it is essential that the subsequent paint or coating adheres effectively to the galvanized surface. Poor paint adhesion can lead to premature coating failure, exposing the steel to corrosion and compromising structural integrity.
Metal treatment methods to increase paint adhesion
Metal pretreatment involves various techniques to create an ideal substrate for the paint to adhere to effectively. They all involve removing contaminants and creating a surface suitable for adhesion by mechanical or chemical methods for example. We will focus here on chemical methods also called chemical conversion or simply conversion.
These technologies includes phosphatation and thin organic coating (or also known as hexafluorides based conversions with Titanium and/or Zirconium).
An important point to note is that no matter the intrinsic performance of the technology used, a poor surface cleaning and degreasing prior to the conversion, will lead to poorer paint adhesion.
Knowing the industry challenges and understanding pros and cons of each metal treatment methods
In today's industrial market, it is extremely important to pay attention to regulatory requirements, cost constraints and environmental considerations.
The choice of metal treatment method must be aligned with the challenges of the sector and the specific requirements of the project, understanding the pros and cons of each method in order to make the best decision.
Zinc phosphatation, for instance, has been renowned for its corrosion resistance and paint adhesion properties. However, it comes with drawbacks such as increasing costs of sludge management, limitations on phosphorus in waste, and the need for stringent bath stability maintenance.
While hexafluoride technologies offer better environmental profiles, they often fall short in terms of corrosion protection and paint adhesion performance.
How to Optimize Paint Adhesion by Using Bifunctional Polymers
Then there are bifunctional polymers - a promising solution for optimizing paint adhesion on HDG steel surfaces. Bifunctional polymers offer an innovative approach that addresses the shortcomings of hexafluorides in terms of paint adhesion performance without affecting their superior environmental profile.
These specialized polymers contain functional groups that interact with both the surface of the substrate and the paint molecules, creating a robust bond that improves adhesion and corrosion resistance of hexafluorides based conversions, making them ideal for use in steel coating applications. Bifunctional polymers like AddibondTM polymers offer ease of application, compatibility with existing processes, and extended bath life, thereby streamlining operations and reducing maintenance efforts.
In conclusion, the quest for superior paint adhesion on HDG steel surfaces has led to the exploration of innovative solutions such as bifunctional polymers. By understanding the importance of paint adhesion, recognizing industry challenges and adopting new technologies, industries can achieve better performance, durability and sustainability in their steel coating applications. Bifunctional polymers represent a promising way to achieve optimal paint adhesion while meeting the evolving needs of the metal treatment market.
