Over the past few decades, consumers have observed many different iterations of waterborne coatings get introduced to the market. Today, waterborne coatings represent the largest class of coatings used globally.
Perhaps it is this great familiarity that many have with waterborne coatings being used for less severe conditions that leads many to believe that water-based coatings cannot be used in high performance environments.
Misconception #1: All Water-Based Coatings are Created Equal
When examining the general category of water-based coatings, it is prudent for one to not look at this grouping of products with a “one-size-fits-all” approach.
In some cases, the performance of these next generation materials rivals or even exceeds the performance of their solvent-based counterparts, as will be illustrated in the commentary to follow.
Misconception #2: Water-Based Coatings Don’t Perform as Well as Their Solvent-Based Counterparts
Water-based coatings are slowly gaining acceptance as confidence builds over time with their increased usage. However, even as recently as less than a decade ago, some have been cited as stating that waterborne epoxy coatings are not as effective as solvent-based epoxies of the same type.
They go on to state that many of these products have only been used on commercial concrete structures due to flash rusting and deficient performance on steel vs. solvent-borne epoxies.
As a rebuttal to this argument, complete water-based coatings systems are now able to meet performance standards such as ISO 12944 category C5 for the highest corrosion resistance. Additional accelerated corrosion tests highlight the high level of performance that the silicon grafted composite topcoats have in atmospheric exposure, as measured by ASTM D4585.
There are even water-based materials now in the marketplace that are acceptable for use in potable water immersion, which was an arena previously occupied entirely by solvent-based and 100% solids materials.
Accelerated laboratory corrosion resistance tests on these materials indicate that many of these innovative water-based technologies either rival or outperform their solvent-based counterparts.
Misconception #3: The Use of Water-Based Coatings Will Cause Flash Rusting to Occur
Flash rust has long been a concern with applicators who apply water-based coatings. However, the coatings industry is seeing the introduction of a wide array of new additives that address flash rusting. These flash rust inhibiting products have varying degrees of chemistry for improved functionality and compatibility in the coating formula.
As a coatings manufacturer, when developing next-generation materials that may contain these new additives, it is important to run thorough testing over blasted steel at the coating’s recommended film thicknesses (min/max to ensure the proper flash rust inhibiting additive and dosage levels helps to prevent flash rusting from occurring during application.
Some of these next-generation water-based materials help to minimize flash rust in other ways. First, these formulations allow for much faster release of the water from the film, which aids in the film formation of these materials.
Also, some variations, especially in the epoxy category, contain cement as part of the formula, which increases the pH, which in turn, helps to minimize the propensity of the steel to flash rust.
Misconception #4: Solvent-Based Coatings are Less Sensitive to Environmental Conditions During Application and Cure than Their Water-Based Counterparts
Waterborne coatings can achieve cure at lower temperatures, down to 40 °F (4 °C). New waterborne coatings can be accelerated, like their solvent-borne counterparts, to speed up their ability to cure, even at lower temperatures.
As previously stated, these next-generation materials allow for faster water release from their films. Once the water has left the film, these materials can cure at very low temperatures and perform at very high levels as it relates to the corrosion protection of the substrate.
Misconception #5: There Are Numerous Application Challenges with Water-Based Materials; Quite Frankly, Solvent-Based Materials Apply with Much Greater Ease
Despite skepticism, water-based coatings can be applied with the same equipment as those of solvent-based coatings. They can be applied with low-pressure airless spray, brush, and roller application.
In most cases, this is a seamless transition for the applicator when moving from solvent-based to water-based materials. The only noticeable difference is the reduction in the amount of solvent that must be utilized on the job site for thinning, cleanup, etc.
Editor’s note: This article first appeared in the February 2025 print issue of Materials Performance (MP) Magazine. Reprinted with permission. The commentary of this article is a sidebar of February’s MP feature, “Water-Based Coatings Gain Popularity for Environmental Benefits,” which can be read in the issue itself.
