Public Lab Research note

Response to Alternative Copper Sheet Preparation Method on Public Lab

by ErikHanley11 | April 12, 2018 02:43 12 Apr 02:43 | #16139 | #16139

I am writing this note as a response to the copper sheet method published by @gretchengehrke. I have also created copper strips for the similar purpose of environmental air quality testing, namely hydrogen sulfide (H­2S). Our methods seem to diverge, so I wanted to compare and contrast.

First, I would like to highlight the advantages of the @gretchengehrke's method. The use of metal cutting scissors when making their copper strips certainly seems to be the superior method. The utility knife I used turned out to be a very arduous process that often warped the copper sheets. The use of metal cutting scissors seemed far easier and resulted in a cleaner cut.

Second, I would like to highlight a couple differences between our methods. The researchers replicated Lionel Milberger's method of sample preparation detailed here. There were a few points in their method that I questioned though. The researchers sanded the copper strips, similar to the copper rod method. However, I believe the purpose of sanding in Milberger's method is to remove manufacturer anti-corrosive layers applied on the piping. Sanding might not be ideal as the copper surface is now variably roughened up between strips, making comparison of corrosion features more difficult. For example, a recent field test at Deer Island Sewage Treatment Plant resulted in our Day 3 copper rod to be the most corroded. The most cause of this difference likely stems from sample preparation where we did not control how much each rod was sanded. Many copper sheets do not have the anti-corrosive layer that exists on the piping, so it is likely unnecessary to sand them.

Additionally, the final step of wetting the copper sheets with acetone and then letting it dry may promote or inhibit the growth of corrosion on the copper sheets. The articles I have read all finish their sample preparation with a wash of distilled water likely because of its neutral characteristics.

I found a comparable copper sheet testing method in an article that prepared their samples using various washes including acetone, isopropyl alcohol, and nitric acid (Demirkan et al.). I replicated their sample preparation, but used acetic acid instead of nitric acid as it is more publically accessible and serves a similar purpose of removing surface oxides. The details of this method can be viewed here. Early results of this method seem to be comparable to Purafil's Corrosion Classification Coupon, a lab-accredited testing method that also uses copper as an indicator for H2S and other sulfide compounds.

I understand that the copper sheet method is still relatively new and welcome any feedback on my own method. I also congratulate the other researchers for approaching a new method for copper corrosion. Their work is valuable in the discovery of the optimal preparation for copper sheet tests.


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