BS EN ISO 3613:2021 pdf download – Metallic and other inorganic coatings — Chromate conversion coatings on zinc, cadmium, aluminium-zinc alloys and zinc- aluminium alloys — Test methods

BS EN ISO 3613:2021 pdf download – Metallic and other inorganic coatings — Chromate conversion coatings on zinc, cadmium, aluminium-zinc alloys and zinc- aluminium alloys — Test methods The sample to be tested should have a surface area of (50 ± 5) cm 2 . For fasteners or samples with a smaller surface area, use a suitable number of samples to obtain the total required surface area. In cases where obtaining a total surface area of (50 ± 5) cm 2 is not possible, a reduced total sample surface area may be used by reducing the water extraction volume, while maintaining the same surface area to extraction volume ratio (1 cm 2 :1 ml). A minimum surface area of 25 cm 2 is recommended. Similarly, a higher sample surface area can be used by keeping the same ratio. The type of adjustment shall be recorded in the final report. Remove any sealing, such as paint or wax, etc., by scraping the surface. The resulting abrasion shall also be analysed. Fill 50 ml of distilled water or water of equivalent purity with anti-bumping granules into a beaker with volume graduation, cover it with a watch glass and bring it to boiling temperature. Let the water boil for at least 10 min to deoxygenate it. Then totally immerse the sample into the boiling water and cover the beaker again with a watch glass. Extract the sample for (10 ± 0,5) min once boiling is resumed. If necessary, add water to ensure that the sample is totally submerged during the extraction. Remove the sample and allow the beaker content to cool to ambient temperature. The solution should be colourless and free of precipitate. Adjust the volume to 50 ml. If necessary, filter the solution through a 0,45 µm membrane filter into a dry beaker. Make up the solution to the mark with water (see Clause 4) or reduce it to the mark by boiling. Add 1 ml of orthophosphoric acid (4.3.2) per 50 ml volume and mix well. Pour 25 ml of the solution using a graduated cylinder into another dry beaker. Add 1 ml of diphenylcarbazide solution (4.3.2) and mix well. Allow the solution to stand for 10 min for the colour reaction to be completed. The remaining portion of the extract will serve as the blank. If there is a colour interference (e.g. from a coating dye), a correction against the...