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Take a good look at your industrial storage tanks. Examine each substrate closely. Do you see a thin, waxy, or greasy film on the surface? If yes, you may be dealing with amine blush.
What is amine blushing in epoxy coatings?
Amine blushing, also referred to as amine exudate, is a chemical reaction between water, carbon dioxide, and the amine content of epoxy coatings. An amine is a compound derived from ammonia. It is hygroscopic, meaning it has the ability to attract and hold onto water molecules from the air.
Amine blushing is a distinct sign of coating failure. As mentioned, it manifests as a thin, waxy, or greasy film on a substrate’s surface, creating an oily or hazy appearance. White or yellow sticky deposits may also arise depending on the amine variety used during epoxy formulation. In some cases, a blush may be undetectable to the naked eye and can only be sensed through touch or a physical inspection.
Why does amine blushing occur?
During the curing process, moisture and carbon dioxide from the atmosphere may react with the amine of epoxy coatings. On occasion, the moisture may also originate from within the porous substrate. This chemical reaction causes amine migration to the applied film’s surface, resulting in an amine blush.
What are the consequences and dangers?
Amine blushing affects industrial tanks by:
- Impairing adhesion quality of subsequent coatings
- Reducing resistance to stains, chemicals, and abrasion
- Lowering gloss retention
- Compromising overall aesthetics
- Raising susceptibility to metal corrosion and tank failure
Are there ways to prevent amine blushing?
Now that you understand what an amine blush is and how it affects industrial storage tanks, let us discuss how to prevent amine blushing.
1. Apply coatings in optimal temperatures
The most effective way to prevent amine blushing is to monitor and control the environmental conditions before, during, and after application. Epoxy coating application within recommended temperature ranges ensures proper curing and reduces the potential for moisture absorption.
An industry-accepted standard is an ambient temperature above 50°F (10°C), making warm and sunny days (not scorching) ideal for coatings projects. Just be mindful of sudden downpours or weather changes where the temperature may drop.
2. Comply with ‘induction time’ requirements
Many epoxies have an “induction time” or “sweat-in time.” It describes the precise duration that must elapse AFTER mixing the epoxy material and BEFORE application (e.g., 30 minutes). This process ensures the epoxy’s polymer chains cross-link successfully. Disregarding the induction time specified in the coating’s product data sheet could result in unreacted or residual amine from the curing process, finding its way upward and outward through the drying film.
3. Enforce humidity control measures during curing
Coating application in environments with low humidity levels minimizes the moisture or dew available for amines to soak up. Using humidity control systems, such as dehumidifiers, can prevent excess moisture absorption during the curing process.
4. Consider ‘force curing’ as a last recourse
In cases where environmental conditions are prone to fluctuation or a project deadline is rapidly approaching, force curing might be advisable. Force curing involves raising the coated surface’s temperature to hasten the cure time.
Conversely, when implementing force curing, avoid heat sources that generate excessive carbon dioxide and moisture, such as direct-fired gas or kerosene heaters. These heat sources can yield the same amine blush repercussions as applying coatings during unfavorable environmental weather conditions. Instead, employ indirect-fired heating systems.
You can learn more about the difference between direct and indirect fired heaters here.
5. Hire a Certified Protective Coatings Specialist (SSPC PCS)
As discussed in our previous post, 5 Reasons You Need a Certified Protective Coatings Specialist, an SSPC-certified PCS offers tank asset owners unrivaled advantages.
As recognized professionals by the Association for Materials Protection and Performance, they exhibit the zenith of aptitude and proficiency in the principles and practices of industrial coatings technology. Reducing the chances of amine blushing and other coating failures is best entrusted to these experienced coatings inspectors, consultants, specifiers, and all-around project managers.
Industrial Inspection Group is home to some of the leading SSPC Protective Coatings Specialists in the United States and outlying territories. Contact us now for assistance in identifying and preventing amine blush from the substrate of industrial tanks.
