Note: This post is part of a larger series on generic coating types. Click the button at the bottom of this post to download the entire guide.
Polysiloxanes are siloxane hybrids formulated with an organic resin such as an epoxy or acrylate systems. These resins combine for characteristics that some professionals are calling the premier finishing coat on the market. When applied as a topcoat on a zinc primer, this system has performed exceptionally in corrosion resistance tests. Later iterations of polysiloxane coatings have been formulated with very high solids, leading to the low VOC numbers now demanded by local and regional regulations.
- Excellent corrosion and chemical resistance
- High UV resistance
- Higher solids and lower VOCs than polyurethane topcoats
- Excellent color and gloss retention
- Have a tendency to become brittle
- Fairly “young” coating still undergoing some experimentation
- Typically more expensive than polyurethanes
Because of their superior UV-resistance characteristics, these coatings have been increasingly used on bridges in recent years. They are also making debuts as topcoats in a number of other industries, including the water and wastewater and marine markets. According to a recent article, heat-resistant properties in some formulations of these coatings have been used in storage tanks, smokestacks and on insulated piping.
The ability to apply a polysiloxane coating directly to a zinc primer has been shown to reduce labor and material costs when compared to zinc-epoxy-polyurethane systems. This could lead to polysiloxanes becoming the industry’s preferred finish coat. However, it is still considered a “young” coating, with certain aspects of its performance still to be proven.