Section 9 Corrosion tests

9.1.1 For all products other than pipes, the material for the test specimens is to be taken adjacent to that for the tensile test and is to be machined to suitable dimensions for either a round or rectangular section bend test. The diameter or thickness is to be not more than 12 mm, and the total surface area is to be between 1500 mm² and 3500 mm².

9.1.2 For pipes with an outside diameter not exceeding 40 mm, the test specimens are to consist of a full cross-section. For larger pipes, the test specimens are to be cut as circumferential strips of full wall thickness and having a width of not less than 12,5 mm. In both cases the total surface area is to be between 1500 mm² and 3500 mm².

9.1.3 Specimens are to be heated to a temperature of 700 ± 10 ºC for 30 minutes, followed by rapid cooling in water. They are then to be placed on a bed of copper turnings (50 g per litre of test solution) and immersed for 15 to 24 hours in a boiling solution of the following composition:

• 100 g of hydrated copper sulphate granules (CuSO₄. 5H₂O)
• 184 g (100 ml) sulphuric acid (density 1,84 g/ml) added dropwise to distilled water to make 1 litre of solution.

Precautions are to be taken during boiling to prevent concentration of the solution by evaporation.

9.1.4 After immersion, the full cross-section test specimens from pipes are to be subjected to a flattening test in accordance with Ch 2, 4.2 Flattening tests. All other test specimens are to be bent, at ambient temperature, through 90º over a former with a diameter equal to twice the diameter or thickness of the test specimen.

9.1.5 After flattening or bending, the test specimens are to be free from cracks on the outer, convex surface.

9.2.1 The material for the test specimens is to be taken adjacent to that for the tensile test and is to be machined to a round or rectangular test piece of thickness approximately 6 mm with total surface area between 1500 mm² and 3500 mm². Any deformed material at the edges is to be removed.

9.2.2 All surfaces of the specimen are to be polished to a uniform finish using 120 grit abrasive paper. Sharp edges are to be removed and, after polishing, the specimen should be thoroughly washed and dried.

9.2.3 The dimensions of the surface are to be measured in order to calculate the exposed area.

9.2.4 The specimen is to be weighed to an accuracy of 0,001g or greater.

9.2.5 For the corrosive media 100g of reagent grade ferric chloride, FeCl₃.6H₂O, is dissolved in 900ml of de-ionised water and filtered to remove insoluble particles.

9.2.6 At least 250ml of ferric chloride solution is to be added to a glass test container. The container is to be placed in a water bath and allowed to reach the required test temperature. The bath temperature shall be monitored and recorded in order to ensure that the temperature is satisfactorily maintained throughout the test. Once the test temperature has been achieved, the test piece is to be placed in a glass cradle and lowered into the solution.

9.2.7 A glass cover is to be placed over the vessel to allow the test piece to remain undisturbed throughout the duration of the test. The standard duration of the test is 72 hours.

9.2.8 At the end of the test, the specimen is to be removed from the solution. It shall be rinsed with water, scrubbed with a nylon bristle brush under running water to remove corrosion products, and then dried.

9.2.9 The surface of the specimen is to be thoroughly inspected to a magnification of x20 and the specimen is weighed to an accuracy of 0,001 g or better.

9.2.10 The results obtained shall be recorded and these shall include the weight loss expressed as g/m² and a description of the surface appearance, noting any evidence of pitting corrosion.

9.2.11 Unless otherwise agreed, the acceptance criteria for the test are that there shall be no evidence of pitting at x20 magnification and that the maximum weight loss shall be 0,8 g/m².