4.1 The ability of a paint or coating to resist degradation of its physical and optical properties caused by exposure to light, heat, and water can be important for many applications. This practice describes artificial accelerated weathering methods designed to reproduce property changes associated with exposure to sunlight, moisture, and heat in end-use conditions. The weathering methods referenced in this practice do not simulate the deterioration caused by localized weather phenomena such as atmospheric pollution, biological attack, and saltwater exposure.

4.2 Cautions—Variation in results may be expected when different operating conditions are used. Therefore, no reference to the use of this practice shall be made unless accompanied by a report prepared according to Section 10 that describes the specific operating conditions used. Refer to Practice G151 for detailed information on the caveats applicable to use of results obtained according to this practice.

Note 2: Additional information on sources of variability and on strategies for addressing variability in the design, execution and data analysis of laboratory accelerated exposure tests is found in Guide G141.

4.2.1 The spectral irradiance of light from fluorescent UV lamps is significantly different from that produced in light and water exposure devices using other light sources. The type and rate of degradation and the performance rankings produced in exposures to fluorescent UV lamps can be much different from those produced by exposures to other types of laboratory light sources.

4.2.2 Interlaboratory comparisons are valid only when all laboratories use the same design of apparatus, lamp, and exposure conditions.

4.3 Reproducibility of test results between laboratories has been shown to be good when the stability of materials is evaluated in terms of performance ranking compared to other materials or to a control material.6^,7 Therefore, exposure of a similar material of known performance (a control) at the same time as the test materials is strongly recommended. It is recommended that at least three replicates of each material be exposed to allow for statistical evaluation of results.

4.4 Repeatability and reproducibility of test results will depend upon the care that is taken to operate the equipment according to Practice G154. Significant factors include regulation of line voltage, temperature of the room in which the device operates, temperature control, and condition and age of the lamps.

4.5 All references to artificial accelerated weathering in accordance with this practice shall include a complete description of the test cycle and equipment used.

1.1 This practice describes artificial accelerated weathering methods for testing the durability of coatings and related products using fluorescent UV lamps and water apparatus operated in accordance with Practices G151 and G154.

1.2 This practice also makes recommendations for preparation of test specimens, exposure duration, and the evaluation of test results.

Note 1: ISO 16474-3 also describes fluorescent UV lamp and water apparatus for artificial accelerated weathering of paints and coatings.

1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.