Polyurethane Primer Outperforms Traditional Epoxy Primers

Spectracron AdvantEdge HPP primer from PPG is a polyurethane primer that breaks new ground in the product category, capable of delivering greater corrosion resistance, edge performance and chip resistance than other available polyurethane and traditional two-component epoxy primers. For steel and ferrous substrates in heavy-duty equipment (HDE), general finishes and transportation applications, Spectracron AdvantEdge HPP primer offers improved performance capabilities while building new efficiency into your priming process.

How? Here we look at the benefits and explanation as to why Spectracron AdvantEdge HPP primer is different—a polyurethane primer like no other.

Competitive Overview

For years, two-component epoxy primers have been recognised as the industry standard for quality control and corrosion protection for heavy-duty equipment, general finishes and transportation applications.

The reliance on two-component epoxies by industry OEMs and their approved outsourcers has historically been driven by epoxy’s proven effectiveness in meeting industry standards for corrosion resistance, as well as their comparatively low cost and ease of use.

Polyurethane primers, meanwhile, have offered users a speedier alternative, typically with better topcoat compatibility and faster wet-on-wet application. But a trade-off was required, as polyurethane primers have traditionally offered less robust corrosion resistance.

And indeed, some coatings manufacturers began in recent years to claim that a two-component epoxy primer is the only product that can affordably achieve the long-term industry-standard corrosion-resistance requirements.

But such claims may not account for some of the limitations of two-component epoxies.

Epoxy primers are only as effective as the pretreatment regimenused before their application. If pretreatment systems are not wellmaintained and managed, even the most advanced primer will notfunction effectively. 

Despite some contentions, two-component polyurethane primers can provide adequate corrosion resistance over properly pretreated surfaces. And for their application advantages, these products have gained popularity in applications where corrosion requirements are less severe.

Two-component epoxy primers require the mixing and addition of a different crosslinking component than polyurethane top coatsto maximise corrosion resistance. This can increase overheadcosts by forcing OEMs and their suppliers to maintain separatecrosslinking-component inventories for epoxy-primer andpolyurethane-topcoat chemistries. 

Epoxy primers tend to be vulnerable to premature degradation when exposed to sunlight for extended periodswithout a top coatfinish. The sun’s UV rays cause the two-component primer tocontinue to self-crosslink, resulting in the primer becoming brittle,chalky or prematurely faded. In extreme cases, this can result incracking and appearance defects, requiring the application to besanded prior to topcoat application. 

In these instances, chalking and fading signal the chemical breakdown of the primer’s base resins and pigments, which ultimately appear as visible losses of colour and/or gloss. The same chemical breakdown associated with chalk and fade also can indicate a similarly negative impact on the primer’s original corrosion-resistance properties.

It points to the need for a primer that can stand up to corrosion while delivering enhanced efficiency and speed to the application process.

New Market Demands

Although two-component epoxy primer systems have a proven history of effectiveness in HDE, general finishes and transportation applications, major OEMs and their suppliers have continued to push the industry to boost corrosion resistance in their finished painted products.

And it’s not just OEMs, as several major factors have highlighted an increasing need for higher corrosion resistance in today’s industrial coatings marketplace. These include:

Globalization. New and emerging global markets have highlighted an emerging need for heightened corrosion resistance. As pieces of equipment are shipped to new parts of the world, many spend considerable time as ocean freight in salt-heavy environments before reaching their final delivery destination.

Prolonged Service Life. OEMs are seeking to take advantage of a hot resale market, enhancing the lasting value of their products—and that means preserving the original appearance and characteristics of that equipment as much as possible.

Consistent Quality Control. OEMs want more control over the quality of pretreated products entering their plants. With a wide and varied degree of pretreatment regimens, stages and levels of maintenance—ranging from simple hand-held application to elaborate multi-stage pre treat with multiple chemistries—pretreatment quality can waver, ultimately affecting finish quality and service life of the end product.

Throughout its history, PPG has worked proactively with OEMs and their suppliers to develop products that meet their needs. In this case, OEMs need an integrated pretreatment, primer and coating system that delivers enhanced corrosion protection while simplifying operations and inventory management. And it must function in unison with multiple, varied pretreatment types and over multiple, mixed-metal substrates.

In short, PPG set out to answer these questions faced by its customers in a changing market with new demands. We put our best scientists and our best chemistry to work to deliver not just an alternative solution to available primers, but a better one.

Introducing Spectracron AdvantEdge HPP Primer

Recently, PPG achieved a significant breakthrough in that pursuit, with the development of Spectracron AdvantEdge HPP primer. Based on a proprietary resin and novel anti-corrosion pigmentation, this patent-pending two-component polyurethane primer provides the following benefits:

Even more significantly, Spectracron AdvantEdge HPP primer is formulated with a common topcoat hardener, enabling OEMs, particularly those using multistage pretreatment processes, to reduce inventory requirements for epoxy and polyurethane primers and eliminate product deficiencies and inconsistencies from tier suppliers and third-party outsourcers.

Although Spectracron AdvantEdge HPP primer is engineered to meet the corrosion-resistance demands of the HDE, general finishes and transportation segments, it also has potential application in automotive parts and accessories and appliance segments.

Extended corrosion protection, edge performance and chip resistance—for steel and ferrous substrates regardless of quality, preparation or degree of treatment.

2,500+ hours of corrosion resistance in salt spray testing per ASTM B117 60+ cycles of cyclic corrosion and edge protection per SAE J2334 1,000+ hours of humidity resistance per ASTM D2247 Excellent chip resistance (7 rating)

Easy, efficient applicability

3- to 5-minute wet-on-wet application, supporting high gloss and high DOI finishes Excellent performance at low and high temperatures and humidities Wide re-coat window—72 hours without sanding, one week with sanding Shared hardener with approved Spectracron 2K polyurethane top coats for improved inventory control

Environmental impact

2.8 lbs/gal VOC (fewer exempts) Low HAPs content REACH-registered raw materials Heavy metal-free corrosion package

Spectracron AdvantEdge HPP Primer: Proven Performance

To demonstrate the performance of Spectracron AdvantEdge HPP primer, PPG performed a range of exhaustive testing—the results of which are detailed throughout the rest of this article.