This practice provides for periodic testing for resistance to wet conditions during storage to compare the relative performance of specific combinations of coatings, substrates, and/or pretreatments used on coil-coated metal. The results must be considered relative and do not indicate absolute performance.

When stored improperly, coil-coated building panel stacks can be exposed to rainwater, which flows into gaps between panels by capillary action or gravity, and remains in the gaps because of poor drainage conditions. Such a condition is known as a “wet stack” and may cause blistering and corrosion of the painted surfaces. This practice simulates such improper storage conditions.

Because the outdoor environment shows year-to-year seasonal and geographic climate variation, the absolute amount of degradation based on corrosion and blistering may vary (see Appendix X1).

Temperature, rain, humidity, and storage practices are important factors in wet stack corrosion. Corrosion and blistering will accelerate with increased temperature. The preferred test location is south of 27°N latitude in Florida. Other locations may be used, but differences in temperature and moisture must be considered, and the amount of corrosion and blistering are expected to vary considerably with climate. Test sites must have the instrumentation to measure and record ambient temperature and rainfall as in Practice G7.

This practice is not meant to support the field storage of coil-coated metal in any way other than what is recommended by the manufacturer.

1.1 This practice is used to determine the resistance to corrosion and blistering of coil-coated metal products relative to one another when stacked outdoors under direct weathering conditions in which they are wetted by rain and dew.

1.2 The coil-coated product variables evaluated may include, but are not limited to, substrates, pretreatments, primers, topcoats, and backers.

1.3 This test simulates a stacked building panel bundle stored at a job site in wet outdoor conditions. The results from panels tested during the same time period at the same physical location may be used to compare products as an indicator of relative field performance. Environments with higher temperature and moisture levels accelerate corrosion and blistering.

1.4 This standard does not endorse the storage of level (that is, 0° from horizontal) building panels stacks in wet outdoor conditions. Level storage of building panels is not recommended and is used in this standard for evaluation only.

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

1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.