Paint Testing & Paint Selection

Tremendous financial losses are incurred every year as a result of premature failure of paints and coatings. Costs of such failures far outweigh the initial costs of painting because of the complexity of repairs and the liability associated with downtime to correct the problems. MATCO's Coatings Division resolves coating failure problems by application of the techniques listed in the table above. MATCO performs a wide array of standard ASTM and NACE test procedures. However, it's not only our equipment that sets us apart from other laboratories, it's our expertise. Our SSPC and NACE certified coating/corrosion professionals will look at the paint failure from both the paint formulation and corrosion/substrate point of views and know which technique will provide the most useful information, given the nature of the failure.

For example, gas chromatography is excellent at detecting solvents, but would be of little use in determining why an alkyd resin failed. Another example is that only EIS and exposure tests can distinguish between storage related problems and paint application/formulation problems in white rust formation on painted galvanized steels. Traditional approaches cannot make the distinction. These insights could save unnecessary effort and expense, simply by selecting the right test.

In our paint failure investigations, you will be kept informed of results as they become available. Each failure analysis investigation will include a formal report containing the description of the defect, review of the application and exposure conditions, chemical analysis of the paint to check against specifications, on-site and analytical test results, factors influencing the paint failure, identification of failure mechanism and root cause, related problems, and corrective actions if requested.

MATCO's Tier Testing assists you in finding the best coating system for your application.

Selecting a coating system that will perform well over time in a given environment is not always a clear cut decision. The type of substrate, service environment, durability, abrasive resistance, and long term appearance are all important factors that should be considered before a coating system is applied.

At MATCO we have developed a stringent “Tier Testing” program that’s designed to test the properties of a coating system when exposed to various environments and conditions in regards to:

• - Barrier Properties
• - Delamination Resistance
• - Impact Resistance and Toughness Resistance to Mechanical Damage & Road Debris
• - Corrosion Protection
• - Color and Gloss Retention (UV resistance)
• - Production Capabilities and Cost Expectations

Our Tier Testing program utilizes the most sophisticated testing techniques available including electrochemical impedance spectroscopy (EIS), disbondment testing, cross section analysis, cyclic exposure, UV testing, gloss and color, gravelometery, and more. Tier Testing is usually performed in either three to four tiers, depending on a coating system’s requirements. Each Tier has specific criteria the coating system must pass in order to proceed to the next level. If a coating system doesn’t pass, it’s not only eliminated from further testing but further cost to the client as well. Clients pay only for the tests performed.

Each tier is designed to test a specific aspect of a coating system’s performance. The first tier tests two of the most important coating characteristics: delamination resistance and coating uniformity, thickness, surface preparation and identification of internal defects. If a coating system doesn’t pass these two important performance parameters, we know the coating system will not provide adequate barrier protection and delamination resistance.

Tier Testing, Level 1: Cathodic Disbondment Testing. Cathodic delamination can be defined as “the destruction of adhesion between a coating and the coated surface caused by products of a corrosion reaction.” This basically means the coating delaminates or lifts and separates from the substrate even though it exhibits good adhesion prior to exposure service conditions .

Tier Testing, Level 1: Cross Section Analysis, above left. Internal defects, such as bubbles or pinholes in the coating, are identified in the first tier of testing. The image on the right shows a high resolution image of pinholes in a coating by SEM analysis for illustrative purposes.

If a coating system passes the first tier, it’s advanced to the second tier which involves cyclic exposure testing and electrochemical impedance spectroscopy (EIS), shown in Figures 2, to evaluate a coating’s performance and ionic barrier properties; adhesion testing prior to and after exposure testing and hot water temperature testing to determine how well the coating system performs when exposed to outdoor higher humidity temperatures in regards to corrosion resistance.

Figure 2: The image on the left shows the electrochemical behavior of a purely capacitive coating (Ideal), while the image on the right shows the electrochemical degradation (from Ideal) of an organic coating. A computerized electrochemical system and EIS software are utilized to collect data and help with analyses. This technique will clearly identify coatings that do not have good corrosion resistance in a relatively short period of time.