What Does Amine Blush Testing Mean?
Amine blush testing is the determination of the presence of carbamates on a coated surface. There are various testing methods; some are easy and quick for field testing, while others are sophisticated laboratory procedures for more conclusive results. Amine blush reduces the coating performance, hence the requirement for testing before proceeding with subsequent coats. The test results help the contractor or applicator determine the quality of the coating and whether to apply the successive coat, remove the blush first if present, or change the application conditions.
Corrosionpedia Explains Amine Blush Testing
Amine blush is the surface exudate, whitish spots or oiliness that develops due to a chemical reaction between the amine curing agent and the water and carbon dioxide in the atmosphere, to form a carbamate.
The amine blush deteriorates the performance of the coating leading to inter-adhesion failures if a new coating is applied on top of the affected coat.
The common test methods are:
- PH testing – the amine blush changes the pH of the coating, which is usually indicated by a change in the color of the test kit. The method is not very accurate since the change in pH can be caused by other factors such as contamination. The method cannot accurately confirm whether the carbonate is present.
- Gas Chromatography–Mass Spectrometry (GC-MS) – a more specific amine blush testing method. The laboratory-based method uses gas chromatography for separating, and the mass spectroscopy to detect the amine blush. The samples are separated into individual components and analyzed using the mass spectrometer. The method is expensive and requires higher technical expertise.
- Fourier Transform Infrared Spectroscopy (FTIR) – involves the focus of an electromagnetic radiation onto the sample. The presence of the blush is usually indicated by the changes in the absorption or emissions of the radiation.
- Elcometer 139 Amine Blush screen testing – based on the presence of carbamate compounds and not on physical characteristics such as the pH. Suitable for lab and field applications, the method is easy and quick, the sample is tested in a test tube or a small vial, and the color change is compared with a known control standard.
The field tests that give instant results are preferred since they allow the contractor to take measures such as the removal of the amine blush or change application procedures to avoid the amine blush and coating failures. In addition, the field test eliminates timely delays due to waiting for the lab results.