Coatings Failure Analysis: Causes and Process Improvements
After investing significant capital into facilities and/or equipment, most business owners commit themselves to preserving their investments. Applying the right protective coating can have a considerable effect on the longevity of the facilities and equipment. However, choosing the right coating requires a critical analysis of the challenges and hazards presented by the substrate’s end use environment and ensuring the coating’s formulation is designed to address these problem areas.
Coatings are comprised of a complex mixture of raw materials and are applied to various substrates, dried, and cured to provide protection from destructive elements—e.g., moisture, heat, wind, cold, humidity, oxidization, ultra-violet, and other environmental factors that breakdown substrate integrity over time. They are available in a variety of forms, including:
Besides providing protection, coatings also affect other material properties, such as:
- Static and electrostatic discharge (ESD) control
- Corrosion resistance
- Flame retardance and heat resistance
- Weather resistance
- Waterproofing and water resistance
A coating failure occurs when coatings no longer perform their designed function—whether practical or aesthetic. This failure often takes place when the bond between the coating and the substrate weakens or ceases.
Causes of Coating Failures
There are four common causes of coating failures:
Proper bonding between the coating and the substrate requires proper surface preparation. If bonding does not occur or is weak due to inadequate surface preparation, a variety of failures or defects may result, including blistering, cratering, crawling, detaching, improper wetting, orange peeling, and uneven gloss.
Improper or Inadequate Application Environment
A broad range of environmental factors during application can also cause coating failures. Variances in air purity, cleanliness, humidity, and temperature often reduce the effectiveness of the bond or cause uneven spreading. Evidence of application environment issues shows up in the form of blistering, wetting problems, solvent popping, and cratering.
Improper or Inadequate Application Technique
One of the factors taken into account during product formulation is application technique. The application of most liquid formulas includes spraying, brushing, dipping, or rolling, but each of these application methods also requires specific techniques and equipment. The failure to apply coatings using their designed techniques results in orange peeling, sagging, or running.
A coating’s formulation must be tailored to the manufacturing process and the product’s end-use environment. If not formulated properly, coatings are apt to fail even when proper surface preparation, application environment, and application techniques are present. Common characteristics of formulation failures include alligatoring, chalking, checking, cracking, erosion, and mud-cracking.
Some examples of using the wrong coating formulation for a product, include:
When choosing a coating formulation, the failure to consider adequate curing time or temperature regarding production speed and environment results in inadequate curing or disruptions in the production process. If your finished products are stacked after painting and are sticking together (blocking), it may be time to reformulate for a quicker cure.
Too Much Material
Improperly formulated coatings often make it necessary to apply thick layers of material or repeat the coating process several times, costing both time and money. In addition, when coatings are applied at a greater film thickness than the specification calls for, it can lead to adhesion issues.
Over-engineered coatings provide properties that are of no value to the manufacturer, often at an unnecessary additional cost.
An under-engineered coating does not meet the production and performance requirements of the manufacturer, resulting in diminished product quality and customer satisfaction.
Preventing Coatings Failures
By making improvements to the coating process, businesses can reduce the likelihood of coating failures and defects, such as:
- Chalking: the development of a dusty material on the coating’s surface
- Erosion: the reduction or elimination of the coating when exposed to environmental elements
- Blistering: the development of small to large bubbles beneath the surface of or within the coating
- Orange peeling: the presence of convex or concave surface texture on the coating surface
- Pin-holing: the presence of small holes through the coating, exposing the surface of the substrate
- Undercutting: the rupturing of the coating due to the presence of corrosive byproducts from the substrate
Some of the process improvements that directly address the primary causes of these (and other) coating failures include:
Improving Surface Preparation
Adequate surface preparation helps achieve a strong bond between the coating and the substrate. The removal of contaminants facilitates proper bonding by eliminating compounds that might contribute to coverage failures, improper wetting, blistering, and other adhesion issues. Operators should understand the type of surface contaminants likely to be present in their process and tailor their precleaning protocols to address these contaminants.
Implementing Process and Equipment Audits
Like any other equipment, paint guns, hoses, spray tips, and other coating equipment wear down over time. Having a standard process for auditing the condition of your paint line can go a long way in preventing issues related to improper coverage or contamination during application.
Encouraging Operator Feedback
Those involved in the process of applying coatings can provide valuable feedback concerning any challenges related to coating application or curing. Using this feedback, manufacturers can adjust coating formulas and application procedures to better suit their production processes.
Using the Proper Formulation
Coating formulation should remain flexible. As facilities make changes to equipment, processes, and materials, coating formulations must adapt to these changes to continue to perform as expected. The coating supplier should work with organizations to custom formulate coatings as their requirements evolve.
Contact Aexcel Corp. Today
Coating failure threatens the longevity of equipment and facilities. Recognizing the causes of coating failure and seeking ways to improve coating performance helps to cut both maintenance and capital investment costs.
At Aexcel Corp., we draw upon our extensive knowledge of standard and custom coating formulation to match the right coatings to the right surfaces and provide the best coating process for each application. In doing so, we help minimize the risk of coating failures.
To learn more about our coating solutions, contact us today.