ISO 17463:2022 pdf download – Paints and varnishes — Guidelines for the determination of anticorrosive properties of organic coatings by accelerated cyclic electrochemical technique.
3.3 cathodic disbonding failure of adhesion between a coating and a metallic surface that is directly attributable to cathodic protection conditions and that is often initiated by a defect in the coating system, such as accidental damage, imperfect application or excessive permeability of the coating [SOURCE: ISO 15711:2003, 3.1] 3.4 cathodic potential E pol potential applied, more negative than open circuit potential, E ocp 4 Principle 4.1 General The initial state of the coating system is characterized by an electrochemical impedance spectroscopy (EIS) measurement (EIS n-1 – see Figure 1). Then the surface is polarized by application of the cathodic potential E pol for a certain period of time, t pol , followed by the relaxation process, r n , over the time, t relax . Finally, the new state of the coating system is characterized by a second EIS measurement, EIS n . These steps define a cycle which can be repeated n number of times (n is the number of cycles). NOTE Typically six cycles are used.
The application of the cathodic potential will generate a stress on the protective coating. If the electrolysis takes place at the interface of the coating to the metallic substrate, the hydroxide ions (OH − ) and/or hydrogen (H 2 ) can cause delamination between the metal and the coating. 4.4 Potential relaxation The purpose of the relaxation process is to allow the formation of a new stable equilibrium before the next EIS measurement is performed. By recording the potential during the relaxation process, valuable additional information about the coating and the coating-metal interface can be obtained. 5 Apparatus Use the electrochemical equipment specified in ISO 16773-2. 6 Specimens 6.1 Samples preparation Proper preparation and preconditioning of coated specimens is critical for successful and reliable experimental data. 6.2 Environmental control The coating should be applied and cured in accordance with the manufacturer’s recommendation unless otherwise agreed upon between the parties involved. The film thickness should be as uniform as possible. The exact film thickness should be measured and reported (e.g. in accordance with ISO 2808). Temperature and humidity control during the application, curing, conditioning and measurement of organic coatings is crucial for a proper determination of the coating resistance. For reliable measurements, temperature control should be equal to or better than ±1 °C. For conditioning prior to measurement, an accuracy of ±2 °C is sufficient for most cases. Each specimen should be kept under controlled conditions in order to prevent post-curing, degradation or any unintended irreversible modification of the coating. The temperature of the specimens during measurements should be maintained constant to within ±2 °C, preferably within ±1 °C, at 23 °C, if not otherwise specified. Relative values for comparison between specimens outside these guidelines are acceptable if all the specimens are run under the same conditions. When the coating capacitance is the main parameter of interest, control of relative humidity during specimen conditioning is very important. To ensure accurate conditioning, the humidity should be (50 ± 5) % in accordance with ISO 3270, if not otherwise agreed. 6.3 Number of specimens and repeatability of results Coatings are materials with certain inherent properties: holidays, inhomogeneous film thickness, and non-uniform distribution of pigments, fillers and other constituents.
ISO 17463:2022 pdf download – Paints and varnishes — Guidelines for the determination of anticorrosive properties of organic coatings by accelerated cyclic electrochemical technique
