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Plascoat PPA 571 - Recommended Quality Control Procedures

Before any coating project is started, a mutually acceptable Quality Standard should be agreed for the item that is to be coated. In such cases, due allowance should be made for any repairs that might be necessary to the finished coating. See "PPA 571 - Repairing Damaged Coatings" for repair methods. The quality standard will require some tests to be performed on some of the coated items. The commonest of these tests are listed below.

2.4.1 Testing the Coating Film Thickness

It is normal to specify a minimum acceptable coating film thickness. This should be sufficiently thick to ensure that there is no risk of pinholes. Any coating film of Plascoat PPA 571 that is above 300 microns should ensure that this would not be a problem. The maximum recommended film thickness is 800 microns. For PPA 571ES 150 microns is the very minimum recommended film thickness. Excessively thick coatings are not recommended since stress cracking may occur. Various instruments are available for checking the film thickness, depending on the metal item that is being coated. Consult Plascoat if assistance is required.

2.4.2 Testing for Pinholes/Porosity

Most finished coatings can be checked for freedom from porosity by using a spark tester. If a high-voltage pinhole detector is used, Plascoat recommends that a test voltage of 1000 volts per 100 microns of film thickness should be selected, up to a maximum voltage of 7,500 volts. If pinholes are discovered, check "PPA 571 - Problem Solving", for possible solutions, and "PPA 571 - Repairing Damaged Coatings" for methods of repair.

2.4.3 Testing the Adhesion of Plascoat PPA 571 - Knife Cut Method

The following subjective method can be used to assess the adhesion of Plascoat PPA 571 coatings: A sharp, pointed knife is used to make two cuts into the coating, penetrating through to the metal substrate and forming converging lines. These should make an angle of 30 degrees. The tip where the two lines meet should be prized up with the point of the knife. The force required to pull off the coating is indicative of the adhesion. If the metal was properly pre-treated and coated, it should be impossible to prize off or lift up the coating without the coating tearing.

Plascoat PPA 571 Data Sheet

Plascoat PPA 571ES Data Sheet