Samples were provided by Benchmark Catalog.
Set-up and test method:
- 2” square samples of the materials to be tested were placed in glass lab jars. Full attention is paid to keeping the set-up clean and sterile.
- Each jar then gets a polished, degreased metal coupon of either lead, silver or copper and a sterile cotton ball wetted with three drops of de-ionized water. Neither the cotton nor the coupon was in direct contact with the test sample, nor touched with bare hands.
- A sheet of aluminum foil topped the jar followed by a tightly screwed on lid.
- For each sample jar, a duplicate control jar was created with the added inclusion of an acid detection strip, but without the moistened cotton.
- One more control jar was made without coupon or sample, but with an acid detection strip added in. This jar was used as a test on the air quality at the time of test prep.
- Prepared jars went into a lab oven held at 35º C. for 28 days.
- Control jars stayed in ambient room temperature of 68º - 70º F. for 28 days.
- After 28 days, the samples were removed from oven. Samples were removed from the jars and examined under a Bausch and Lomb Stereo Microscope 10x magnification using a raking full spectrum LED light. A color card was also used to determine any subtle changes to the materials.
- Pass/Fail was determined by a visual evaluation. A sample received a “pass” when the coupons had no more corrosion than the corresponding control jar.
- A “fail” was earned by corrosion of some sort different from anything found on the control coupons.
Types of corrosion:
- Silver is corroded by reduced sulfur-compounds and carbonyl sulfides. The coupon will turn black and, in extreme instances, pitting and etching of the surface is evident.
- Lead is corroded by organic acids and aldehyde and acidic gases. Corrosion is represented as a powdery white to a reddish brown material on the surface of the lead coupon.
- Copper is corroded by chloride, oxide and sulfur compounds. Corrosion shows on the coupon ranging from dark brown to powdery green or whitish precipitate.
- A-D strips alter color, turning from dark blue to green to yellow when exposed to an acidic environment and, therefore, pH is established. (This can be evident within 24 to 48 hours after start of test.)
Requested by Benchmark, Rosemont, N.J. 08556