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Saltwater staining and silver nitrate test
Q. Bundled steel pipes, covered in protective wrapping were carried on open trucks from factory to dockside, 72 miles over metaled and unmade roads. The dockside was unmade (i.e. pitted, muddy and with deep puddles). Rain was intermittently heavy over seven days' loading onto vessel. Loading was stopped during heaviest rain. The sea passage to discharge port was eight days'.
On discharge considerable rust staining was noticed on that wrapping that was intact. In part the wrapping had torn during passage. A proportion of the steel pipes were so badly rusted (about 25% of total) that they were not accepted by buyer. A silver nitrate test was conducted three days' after unaccepted cargo had been discharged and stored in sheds at dockside.
The test revealed the presence of chlorides by vigorously producing a creamy foam. Not all damaged pipes tested positive for chlorides.
What does the test show? Can the test indicate the origin of the chlorides? In this circumstance, what else might the results of a silver nitrate test indicate?John [last name deleted for privacy by Editor]
- London, Great Britain
A. Hi, John.
Unfortunately, I think the test shows that at the time of the test there were chlorides on the parts and nothing more. Sorry :-(
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Dear Sirs,
Please certify the concentration of AgNO3 in ammonium solution for proper saltwater test on steel surface and corresponding contest of chlorides.
- St.Petersburg, Russia
A. DEAR IGOR
The basis of the test is that a liquid containing chloride ions changes immediately into a whitish solution when silver nitrate solution is added (0.1 mol/L). If these chloride ions are not present, the solution remains clear and transparent.ALEKS PANFILOV
Q. Can silver nitrate tests be accurate below 40 degrees F?Matt Salkeld
Surveyor - New Orleans, Louisiana