ASTM G9-07 (2020) pdf free.Standard Test Method for Water Penetration into Pipeline Coatings.
Energize each specimen by connecting it to the negativeside of the voltage source. Keep each sample energized andimmersed to the lower edge of the upper end cap for theduration of the test period. Maintain the specified electrolytelevel through regular additions of tap water.
Throughout the test make periodic measurements of theseries capacitance and dissipation factor of the immersedspecimens in the following manner:
Temporarily disconnect the test specimen from thevoltage source. Verify that the electrolyte is at the proper levelwithin the immersion cell. Connect the measuring bridgebetween the test specimen and stainless-steel anode. Energizethe bridge and measure the series capacitance,C, and dissipa-tion faction,DF, of the test specimen.
Using the observed value of series capacitance，Cs.calculate the apparent depth of water penetration by the methoddescribed in 9.2.
Repeat the measurements of series capacitance andspecimen dissipation factor at periodic intervals throughout theduration of the test. The frequency of measurement will dependupon the rate of deterioration of the coating sample. Where thewater penetration process is relatively rapid, daily readings ofsample capacitance and dissipation factor will be required.Normally,readings made at weekly intervals will adequatelydefine the penetration rate.
The test specimen shall be a representative piece ofproduction-coated pipe and shall be free of obvious coatingflaws or defects (see Fig.3). Any suitable diameter andspecimen length can be used. Physical limitations of theimmersion cells suggested in 5.1.3，Note 1, make it necessaryto restrict the overall sample length to approximately 300 mm(12.0 in.) for both the 19-mm (0.75-in. nominal) and 51-mm(2.O-in. nominal) diameter coated pipe specimens.
The upper and lower ends of the test specimen shall beplugged and sealed with nonconductive caps of sufficient bulkto minimize effectively capacitive end effects in the measuringcircuit. For this purpose, an end-cap thickness of from 13 mm(0.5 in.) to 19 mm (0.75 in.) shall be maintained.
The end-cap material shall have a dielectric constantin the range from 2 to 6, bond well to the coating surface, andexhibit a low water-absorption rate. Several commerciallyavailable poly(vinyl chloride)-paraffin compounds，are wellsuited for this purpose. They have a melting point in the 150 to200°C (300 to 390°F) range,can be poured into molds aroundthe pipe sample, and appear as resilient, durable solids at roomtemperature.ASTM G9 pdf download.