PPG Integrated Coatings Layers Delivers Next-Level Coil Protection and Performance

By Shelley Verdun

The economic toll of corrosion is staggering. In the most recent U.S. corrosion study, the direct cost of metallic corrosion was estimated to be around $276 billion annually, about 3.1% of the U.S. GDP. 

Whatever the source—high heat, humidity, UV rays, moisture, and wear—the electrochemical reaction that leads to rust, oxidation and substrate degradation is a threat to the service life of metal components in the environment.

To help guard against corrosion, as well as to protect against chips, abrasions, and fading, leading coatings manufacturers like PPG are continuously engineering new solutions that take substrate protection to the next level.

Liquid, Powder, or Both 
Layering is the key to a more robust protection system. Typical solutions for metal parts include two-coat systems with a primer coat for corrosion protection and topcoat for color, appearance, and UV resistance. Other options include one-coat hybrid systems that combine a mixture of resin chemistries to provide an optimal balance of corrosion protection and UV resistance.

Liquid coatings use solvents or water and are applied to pretreated metal with electrostatic spray, dipping, and other conventional methods before being air-dried or force cured.

When used as part of an integrated primer, pretreatment, and topcoat system, liquid coatings offer exceptional resistance to corrosion and chemicals, excellent sag resistance and strong adhesion. Newer product offerings in waterborne liquid technologies offer a more sustainable option as part of an integrated coating layer.

But manufactures and fabricators are increasingly turning to powder coatings for its performance, aesthetics, and sustainability advantages. In fact, powder is the fastest growing coating technology in the world.

Powder provides excellent hardness, corrosion resistance, and chemical resistance, but also offers broader design options than other technologies including unique finishes such as hammertones, granites, and microtextures.  It is also considered to be a more sustainable coating platform since there are virtually no volatile organic compounds (VOCs) within the product or application process. Powder can also be reclaimed and resprayed and requires only compressed air for clean-up. 

PPG has recently developed a new layering system that utilizes a coil coating liquid primer, followed by a powder topcoat. This system not only elevates the corrosion resistance performance of metal parts with an added layer of protection, but also streamlines the production process for manufacturers.

A Better Coil Cleaning and Coating Process
Many fabricated metal parts start with steel that has been flattened into sheets and then rolled into coils. The coils are then often sent to a fabricator or manufacturer to be stamped or shaped into parts before finishing.

In coil-driven industries like HVAC, building products, and transportation, it is common to use a one-step, direct-to-metal (DTM) powder coating process.

This process, however, requires that manufacturers perform a complete cleaning and rinsing of the metal so all traces of oil, lubricants, dust, dirt, and contaminants are removed. Cleaning the substrate is critical to ensure good adhesion of the powder across all areas of the part.

PPG has recently developed a Coil Primer-Powder Topcoat (CPPT) layering system that eliminates the important yet laborious cleaning function for the manufacturer, saving them time and money by eliminating the need for cleaning chemicals, hazardous wastewater removal, and the labor needed in the process. 

Primer + Powder Topcoat Takes Corrosion Protection to Next Level
Developed by PPG scientists, the two-layer CPPT system replaces the standard DTM powder process with the addition of a thin-film, durable liquid primer basecoat.

Instead of coiled steel being sent directly to the fabricator or manufacturer, they are first shipped to a coatings applicator where they are unrolled, cleaned on both sides, coated with a primer and oven cured. The sheets are recoiled and packaged for shipment, ready for immediate powder coating application and fabrication. 

The result is a more streamlined production process that increases throughput, makes compliance with environmental regulations easier to achieve, and adds an extra layer of corrosion protection with a factory-applied, baked on primer that extends the lifecycle of the parts.

This proprietary two-coat system includes a urethane liquid primer, followed by an ultradurable polyester powder topcoat with high transfer efficiency (HTE) properties.

Polyester powders offer appealing benefits to the industry with excellent UV-, humidity- and weather resistance, hardness, high first-pass build rates, flexibility, and abrasion resistance.

The HTE formulations offer additional advantages:

• Up to 85% first-pass build rates that reduce labor, material, and utility costs.
• Improved wrapping on complex parts for fewer rejected parts and touch-ups.
• Better control of powder film thickness so less powder needed for full coverage.
• Reduced energy needs with lower baking temperatures (10/350° F or 20/320° F).
• Good penetration on complex parts, shapes, and recesses.

Layering Expertise for Lasting Performance 
Newer generations of coatings and coatings systems can extend the lifecycle of metal components, reduce warranty claims through enhanced corrosion resistance, and streamline the manufacturing process.

PPG is one of the top innovative coatings suppliers in the world and provides solutions for every layer of protection in all major coatings platforms—pretreatment, electrocoat, liquid, and powder. 

As a total integrated solutions provider, PPG has expertise in the entire coatings process, along with a wide range of products and resin chemistries that have been tested according to standard industry criteria.

Additionally, PPG’s coatings services business specializes in application services through a network of offsite regional coating centers or in-house paint line management, as well as equipment design, engineering, and installation expertise. 

PPG has a global presence and partnerships that span a wide range of industries. This broad expertise, along with dedicated lab resources, can help manufacturing partners identify the best test methodologies to measure a product’s potential service life, quickly correct coatings failures, and troubleshoot general coatings-related production problems. 

For more information on this and other PPG innovations, please visit the PPG website.

Shelley Verdun is PPG’s Business Manager for Industrial Coatings. She has been a part of the coatings team for more than 33 years and has helped to lead the company’s growth as a coatings leader across the world, specifically in North and South America.