From electronics to shoes and fabrics, water resistance is a characteristic expected of many consumer goods. It is also required from industrial machinery and architectural structures. A water resistant coating is the most common solution for creating or improving water resistance in industrial and architectural projects. Water resistant coatings form a barrier between the substrate and its environment; depending on the water resistant treatment, the barrier can be impermeable to water; whether liquid or vapour.
In this article we define the different types of water resistant coating systems, explore the options for different industrial and architectural applications, and state the most common issues regarding water resistant treatment of surfaces.
Water resistant versus water repellent versus waterproof
Though the terms ‘water resistant’, ‘water repellent’ and ‘waterproof’ are often used as synonyms, they actually describe different degrees of water resistance. Water resistant coatings can be classified by the the level of protection from water as follows:
- Water resistant: Usually the lowest degree of water resistance. Able to resist water penetration to a certain extent, but not entirely – in most cases a ‘water resistant’ product cannot be completely submerged without problems. ‘Water resistant’ is also the general term for water protective coatings.
- Water repellent: Higher resistance than ‘water resistant’, yet also not completely impermeable to water. Often refers to nano- or fluoropolymer coatings which literally repel water.
- Waterproof: An almost 100% watertight solution, these coating systems are absolutely impermeable to water.
Despite the difference between waterproof and water resistant, consumer products may still be called “waterproof” when they are only resistant, and vice versa. But these are descriptions that can apply to more than just coating. When choosing a coating, you should always check the manufacturer’s data sheets and instructions.
Selecting the best water resistant coating for your project
Waterproofing products are as various as waterproofing projects. However, not every water resistant coating suits all situations; like with all coating projects, you need to consider the intended substrate, use, and environment of the coating, as well as that the required degree of water resistance. For example, a water resistant coating for fabric needs to be invisible, electronics require thin films, and steel requires an impermeable barrier to protect from corrosion. On the other hand, a waterproof wall paint never is 100% watertight, due to the fact that it needs to remain breathable.
Here are four of the most common water resistant coating solutions:
Characteristics: Corrosion resistance, limited water resistance.
The treatment of a metal surface with another metal in processes like galvanisation and anodisation is seen as an effective corrosion protection method in certain environments. These processes also provide water resistance, to a certain extent, by covering the original metal substrate. However, this is often not sufficient, so to conform to tougher waterproofing requirements it is topped with a resin or fluoropolymer coating.
Applications: Steel structures and products, in tougher environments as pretreatment with a further topcoat.
Characteristics: Insulating, impermeable to gases and water, resistant to chemicals, UV radiation, contamination and chalking as well as anti corrosion
Fluoropolymer coatings are known for their low coefficient of friction and use as lubricants. The most common of these are FEP and PTFE coatings such as Xylan and Teflon which are almost impermeable to water. Fluoropolymers are also the most common type of Durable Water Repellent (DWR) coatings which are applied to fabrics as waterproof yet breathable coatings.
Applications: Consumer goods, industrial machinery, automotive parts, insulation of wiring, fabrics.
Characteristics: Durable, impact and abrasion resistant, watertight, chemical resistant and many more beneficial properties depending on the type of resin coating
Two component resin coatings such as polyurethanes and epoxies belong to the most durable water resistant coatings group. Such a coating is almost always a good idea, and there are many different types which can be further modified to meet specific requirements.
Applications: Pools, vertical and horizontal architectural structures (from bathrooms to offshore wind turbines), cargo and storage water tank lining, machinery and automotive parts.
Characteristics: Thin, transparent, water repellent but lacks abrasion resistance
The most innovative water resistant coatings are based on nanotechnology, and do not just coat a substrate but actually bond with it, forming a layer that is no longer separate. The use of these coatings, especially in waterproofing industrial structures, is increasing and the technology keeps developing. Nanotechnology coatings also exist as water resistant spray treatments that are available for consumers to apply at home.
Applications: Touchscreens and displays, small surfaces at home (e.g. windows and shower cubicles), protecting wooden floors from water.