ISO 21746:2019

ISO 21746:2019 pdf free.Composites and metal assemblies——Galvanic corrosion tests of carbon fibre reinforced plastics (CFRPs) related bonded or fastened structures in artificial atmospheres——Salt spray tests.
5 Apparatus
5.1 Component protection. All components in contact with the spray or the test solution shall be made of, or lined with, materials resistant to corrosion by the sprayed solution and which do not influence the corrosivity of the sprayed test solution. If necessary, electric insulation shall be devised for the apparatus to prevent the influence from inside or outside of the apparatus. The supports for the test specimen shall be constructed such that different substrate types do not influence each other. It shall also be constructed so that the supports themselves do not influence the test specimens.
5.2 Spray cabinet. The cabinet for galvanic corrosion test shall be such that the conditions of homogeneity and distribution of the spray are met. Due to the limited capacity of cabinets smaller than 0,4 m3, the effect of the loading of the cabinet on the distribution of the spray and temperature should be carefully considered. The sprayed solution shall be fell down naturally on the test specimens, and the upper parts of the cabinet shall be designed so that drops of spayed solution formed on its surface do not fall on the test specimens being tested (see Annex A]. If a cabinet for galvanic corrosion test has been used once for an AASS or CASS test, or has been used for any other purpose with a solution differing from that specified for the NSS test, it shall not be used for the NSS test. The size and shape of the cabinet shall be such that the collection rate of solution in the cabinet is within the limits specified in Table 3, measured as specified in 9.3. Preference shall be given to apparatus that has a means for properly dealing with fog after the test, prior to releasing it from the building for environmental conservation, and for drawing water prior to discharging it to the drainage system.
5.3 Heater and temperature control. An appropriate system for galvanic corrosion test maintains the cabinet and its contents at the specified temperature (see Table 3). The temperature shall be measured at least 100 mm from the walls.
5.4 Spraying device. The device for spraying the test solution comprises a supply of clean air, of controlled pressure and humidity, a reservoir to contain the solution to be sprayed, and one or more atomizers. The compressed air supplied to the atomizers shall be filtered to remove all traces of contaminants such as oil or solid matter, and the atomizing pressure shall be at an overpressure of 70 kPa to 170 kPa. The pressure should be 98 kPa士10 kPa. In order to prevent the evaporation of water from the sprayed droplets (aerosol), the air shall be humidified before entering the atomizer by passing through a suitable humidifier. The humidified air shall be saturated such that the concentration of the fallout solution falls within the specifications of 4.1. The humidified air shall also be heated such that when mixed with the salt solution, there is no significant disturbance of the temperature in the cabinet. The appropriate temperature depends on the pressure used and on the type of atomizer nozzle. Temperature, pressure or humidification, or a combination thereof, shall be adjusted so that the rate of collection of the spray in the cabinet and the concentration of the collected spray are kept within the specified limits (see 9.3). A common used humidifier is the saturation tower, where temperature and pressure are controllable. Table 1 gives guidance values on temperature and pressure combinations for the saturation tower.ISO 21746 pdf download.

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