Analysis of the Effect of the Second Thickness Layer or Intermediate Layer on the Three-Layer System on Adhesion Strength on Carbon Steel Surface

Generally, the marine & offshore industry uses a wide range of coatings, both liquid and thermal, which aim to protect or inhibit the rate of corrosion of materials in the surrounding environment. Referring to the Norsok M-501 standard, there is a Coating System Data Sheet (CSDS) that provides an overview of the coating system according to the surrounding environment. In CSDS 1B, a three-layer system is employed, consisting of a zinc-rich epoxy primary layer, an epoxy intermediate layer, and a UV-resistant top layer. The specification provides the thickness of each coating layer from the first layer to the top layer. However, during the fabrication process, there are some challenges that occur with the second layer, which is epoxy. Sometimes, during the application of the second layer, the thickness of this layer is less than or more than the specified thickness. This study aims to determine the effect of the thickness of the second layer (intermediate layer), namely epoxy, on the adhesion of the three-layer system. This research will be carried out through experimental testing with variations in the thickness of the second layer (intermediate coat) of 50, 100, 150, 200, and 250 microns. The adhesion test for the second layer will use the X-Cut Tape Test and Pull-Off Test methods. The results of the adhesion strength test show that the thickness of the second layer affects the adhesion value of the coating system itself; The thicker the intermediate layer, the worse the adhesion strength, or there is a decrease in adhesion strength. This is supported by the test results on panel 1 with a second layer thickness of 50 microns, which obtained an average tensile test result of 18.37 MPa, and on panel 5 with a second layer thickness of 250 microns, which obtained an average tensile test result of 14.19 MPa.