PVDF Coatings are a common industrial standard for metals, especially aluminum. These plastic-based coatings offer unparalleled benefits for the base metals, and almost every aluminum site has a PVDF coating.
More on the benefits later! You’ve probably seen PVDF coating before but are unfamiliar with the terminology, or maybe you’re trying to weigh out the different coating options available.
In this article, I will share deep insights into PVDF Coatings, their uses and benefits, and the professional experience that helps our clients decide between PVDF coating and powder coating.
What is PVDF?
PVDF coating or PVDF is an easier acronym for Polyvinylidene fluoride, which is a non-reactive plastic from the fluorocarbon family, used to enhance the properties of metals, typically their shelf life.
PVDF belongs to the fluorocarbon family making it a thermoplastic with some unique properties.
According to a scientific journal on MDPI, PVDF resin
- Can withstand temperatures around 100 ℃
- Is ductile and flexible
- Recyclable and non-toxic
- Fire resistant
- Unreactive with petrochemicals and acids
These properties make polyvinyl fluoride a highly sought-after coating for metals and the use of dyes and pigments makes it ideal for architectural aluminum. PVDF is the second highest used fluorocarbon after PTFE or Teflon.
PVDF coatings were popularized because of their use on aluminum surfaces. Aluminum is widely used in architectural structures, cladding, roofing, and curtain walls which need an extra layer of protection from weather damage and harsh external conditions.
PVDF coating on aluminum surface is a resin-based coating system with good adhesion to aluminum surface and thermally stable bonding with an unreactive chemical nature.
PVDF Aluminum Coatings Manufacturing Process
PVDF Coatings manufacturing process involves a set of identical steps followed worldwide but the quality of PVDF fluoropolymer resin can be altered by manufacturers to better suit your particular use and requirements.
Some compositions are even tuned for aesthetics. This includes adjusting the pigment and solvent ratios.
Before getting into the PVDF coating process here’s a quick look at the PVDF coating composition.
PVDF Coatings can be easily colored for aesthetics.
In fact, it’s a viable solution to painting over aluminum which is not as long-lasting. There are many color choices and finishes from organic to metallic colors which determine the color retention and durability.
Resins make up for most of the coating thickness. Resins bind together the pigment and adhere to the aluminium surface. They also contribute to the performance of PVDF coatings.
Adding a solvent to the mixture makes the application of the PVDF coating possible. They decrease the viscosity of the resin and allow it to uniformly cover the metal surface. Acetone is a common example.
The choice of additives depends on the manufacturer and trademarked PVDF coating. Additives affect the coating’s resistance, thermal performance, UV resistance, rust resistance, gloss, and other features.
PVDF Coating Process
After selecting the proper proportions of PVDF coating and adjusting the opacity through pigment, the PVDF Coating Process constitutes the following steps.
1. Surface Preparation
This is the most important step for the PVDF coating process. Aluminum surface is degreased using alkaline cleaners and later scrubbed and brushed to remove any scale and dirt. To remove rust, chemical agents like acid are used and the substrate is rinsed thoroughly.
A primer is used on the raw substrate before the coating. This prepares the aluminum for the top coat, and improves adhesion and surface evenness for a neat coating.
3. Top Coat
Top coat is the thickest layer on the aluminium substrate. Top coat holds the resin mixture manufactured prior to PVDF coating process. Once poured pigment can further be added for aesthetic accuracy. The top coat directly impacts the durability, abrasion resistance, corrosion properties, and UV resistance.
Since resin-based coatings use a solvent, it is important to cure the coating after this step so the solvent evaporates, leaving the top coat and aluminum surface to adhere.
4. Clear Coat
Clear coating is important to ensure the PVDF coated substrate will last. Clear coating prevents the pigment from easily fading under constant exposure to the sun and acts as a preventive layer holding the entire coating together. Clear coat is thinner than all other layers of PVDF coating.
How Is PVDF Coating Done? How Thick Is PVDF Coating On Aluminium?
You might be wondering how is PVDF coating applied to aluminum? Is it poured onto aluminum and spread or is it like painting with a standard brush? Well, PVDF coatings require special application tools for an optimum layer.
The choice of application depends on coating thickness and type of aluminium product. Here are the common PVDF coating methods currently used.
Bear in mind, that these processes are automated and primarily done in bulk to minimize material loss.
Spray coating PVDF onto aluminium surface involves a manually controlled jet with pressurized air that can be maneuvered by the user. In large-scale industries, robotic bells and robotic guns perform the same operation with consistency, and even thickness of PVDF coatings on metal surface.
From our professional experience at Wellste, spray coating flat aluminium surfaces, such as aluminium sheets, can result in slight warpage due to the curing temperature. To avoid this take a look at other processes and our aluminum extruded profiles.
Many PVDF coatings involve multiple passes of the top coat for uniform coverage. This process is usually done on metal roofing and automobile parts.
Coil Coating PVDF involves coating rolls of aluminum at the factory. Coil coating is superior to spray coating because it is a continuous process that ensures PVDF coatings before aluminum is shaped into aluminum extrusion, cut into sheets, or shaped into another form.
Coil coating involves roll coating, where PVDF coatings are applied to aluminium coil passing through rollers. Thickness of coil coatings can range from 0.2 mm to 1.6 mm.
PVDF Aluminum Applications
PVDF coatings are widely used for their many benefits. Some of the uses you might not know of are included in the list below.
PVDF coatings are most commonly seen on modern buildings.
Spray PVDF-coated panels are installed onto a building’s face because they offer corrosion resistance, and protection from UV rays. These panels are long-lasting that often do not need to be replaced for decades.
Metal roofings are prone to weather damage and temperature fluctuations. PVDF coatings on metal roofings offer protection from weather elements, corrosion resistance, and abrasion resistance.
Aerospace and Aircraft Applications
Aluminium components are widely used in airplanes and PVDF coatings offer excellent resistance from weather and improved abrasion resistance where needed.
Curtain walls are used in glass buildings as a non-structural addition. Curtain walls wrap around the exterior of the building are exposed 24/7 to sunlight, water and high temperatures.
PVDF coatings are light and do not change the dimensions of these aluminium claddings which makes them optimal as protective layer that is sunlight resistant and can sustain temperatures.
PVDF Vs Powder Coatings
There are other alternatives to polyvinylidene fluoride coatings and powder coating is among the cheaper ones with similar applications.
However, you should know about the key differences which can help you decide on one for your project needs. Alternatively, you can reach out to our online queries.
|PVDF Coating||Powder Coating|
|More durable and resistant to weathering, UV rays, and chemicals||Not as durable, and most fade or give away with time.|
|Better color adhesion and gloss||Mostly matte finish|
|Thinner||Powder coatings are thicker|
|Curing possible at room temperature||Powder coating curing requires oven|
|Liquid-based coating||Powder based coating|
|More expensive||Cost-effective and ideal for prototypes and single projects|
|Uses solvents which lead to environmental impact||Powder coating is more environmentally friendly as there are no volatile organic compounds involved|
Other alternatives to PVDF and powder coatings include chrome-based conversion coating like anodizing and alodining aluminium surface.
Why choose PVDF coating for most buildings？
As building owner, you’d want to preserve the exterior and look of your building as much as possible.
While aluminium curtain wall offers a clean and ideal solution to holding glass panes and creating external surfaces, they need to withstand the constant weathering and remain exposed to the sun for long periods.
PVDF Coatings offer minimal maintenance with a one-time investment. Manufacturers can use additives and multiple layers of coating to adjust the resistance against weathering as PVDF coatings have UV-resistant, thermally stable, and chemically inert properties.
PVDF coatings are made of plastics with anti-fading and great adhesive properties. Thanks to their chemical bonding, they are unreactive with petrochemicals and fire resistant.
Furthermore, they can make use of pigment to provide any color to aluminium surface and can mimic a metallic luster when needed.
They are better than powder coatings and other variants of surface protection for aluminum and remain a highly sought-after industrial process to prolong the life of metal.