Field Testing for Soluble Salts

A Problem to Be Aware Of

From JPCL, September 2020

By Simon Hope, Auquharney Associates Ltd.

The presence of soluble salts on a surface is a major factor in premature breakdown of protective coatings, and resultant increased maintenance costs for the asset owner. This article explains why the presence of salts are a problem, how to measure for salts on a surface, industry standards on the subject and the results of a case study involving salt detection and removal....

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Comment from Regis Doucette, (9/21/2020, 9:24 AM)

Thank you for providing solid wisdom here about an infrequent topic of non-visible contaminants that make very frequent appearances in the field. Testing for soluble salts is a two-step process of extraction and analysis. Your presentation is spot on about the various methods. Extraction of surface ionic contaminants using distilled water, documented in numerous studies, will solubilize but half the tests out there which means half the samples are inadequate. Thus, at the analysis stage, investigators/field tests will be starting off with half the tests not able to identify the problem. This condition or problem is akin to having someone who lies to you half the time, but you cannot discern which half of the time he/she is telling the truth. The second part of testing is the analysis which you presented so very well. Conductivity, be it a patch or an app on a mobile device with fancy electronic displays like Teddy Ruxpin, measures a bundled value of all conductive constituents and not the true cause of the corrosion. Engineering is defined by calculations, not assumptions and inferences when real data is available. Ion SPECIFIC testing is critical to fighting corrosion as it is definitive and not inferential. In my presented paper, “Defeating the Fifth Column of Corrosion by Properly Detecting Non-Visible Contaminants with Ion Specific Testing Versus Conductivity”, I gave many real world examples, specifications, and historical context, as you have ably done here. Keep up the great work.

Comment from Simon Hope, (9/22/2020, 1:58 PM)

Thanks for the positive comments Regis, the taking of high risk testing from the lab and into the field and being given to people who don’t fully understand what is actually being done is a great worry.

Comment from Dave Wonnacott, (9/22/2020, 7:37 PM)

This is an excellent article. Thank you Simon. Why not prep a surface with a gelled acid that removes a small amount of the surface material and it's contaminents?

Comment from gavin bowman, (10/26/2020, 5:11 AM)

Excellent article Simon, certain aspects have backed my thoughts up from when I became a 'Salt Nerd' a good while ago!

Comment from Gunnar Ackx, (10/27/2020, 3:01 AM)

Ask much as I believe in 'ion-specific' testing vs the 'general' Bresle Method, we did a project a couple of years ago involving the requirement to perform several hundred 'ion-specific' sleeve-tests, measuring Chlorides, Nitrates & Sulphates, which EVERY single time came up as ZERO or 0,1 µg/cm2. When running a Bressle test against it, we mostly had between 10 & 20 mg/m2 (1 to 2 µg/cm2), still within specifications, but a difference of 10 - 20x with the 'ion-specific sleeve test'. Factors such as contamination of patches, sampling water, gauges, etc... were all ruled out because we have very extensive experience with the Bressle-test. Our conclusions: a) whilst the Bressle-method may be measuring ALL ions, this method seems to have a higher resolution (at low levels) than the 'ion specific sleeve-tests' which seem to have poor resolution, especially in the low end of the range b) regardless of manufacturer claims about equivalence between Bressle and other 'conductometric' measurement devices (e.g. using filter paper) or ion-specific sleeve-methods, we have NEVER been able to come up with comparative test-results when testing them next to each other. So, not saying the ion-specific sleeve-test is better or worse than the Bressle, but people should be aware that there is NO correlation between the different methods. My 2 cents worth on this (indeed) important topic.

Comment from Tom Swan, (10/28/2020, 10:58 AM)

There is no correlation between ion specific testing and Total salts testing because they are looking for two, related, but different things. If you look at the history of the "CSN" test, it was developed specifically to NOT find all the salts. The manufacturer of a certain product was having issues that after their product was used, the total salts would often be higher than before they used their product. Since there were no "C,S or N" in their product, by only testing for the three ANIONS, they could show that their product removed these three anions from the surface and thereby consider the surface as clean. There may be situations where specific ion testing is justified but just because there are no Chlorides, Sulfates or Nitrates does not mean there are no "salts". This industry treats CSN and equal to total salts. CSN are not salts. Specifically they are half of a salt, the anion. This industry tends to ignore the cation. If I have my choice between running one test, it will be total salts. There may be instances where a specific ion test is required to quantify a problem as describe in the article, but it should not be used to replace a total salts test. - There is no correlation because they are not the same.

Comment from Peter Bock, (10/29/2020, 8:50 AM)

The biggest problem with all the salt (and ion--thank you Tom Swan) testing is that it tests only very small spots and the type and amount of contaminants on the surface can vary widely. In the early 2000's, when I worked for a very large industrial coatings company that was willing to spend money on lab work, we did dozens of Bresle tests on different spots of the same 300 sq. ft. section of contaminated tank wall. The test results varied widely, even between adjacent test areas. What we need is a test instrument like a paint roller or a low voltage holiday detector, which can sweep large surface areas and do large numbers of salt or ion tests, producing a map, or at least an average, for the whole tested surface. Until then we are really still just guessing and hoping.

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