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April 2 - April 6, 2018

Under what types of exterior atmospheric exposures (other than marine) is it necessary to test for soluble salts?


Selected Answers

From trevor neale of TF Warren Group on April 9, 2018:
I would add to John's excellent comments that steel being transported by road on open trucks during the winter seasons where salts may be used to de-ice the roads should be checked as part of the surface preparation sequence. In fact, as Norman has stated, unless we know the source of the incoming or existing surface, all should be viewed with suspicion and verified for cleanliness.

From Norman Petticrew of Chlor*Rid International, Inc. on April 4, 2018:
Well written Mr. Brodar! I thought you had covered basically everything, but when I read Mr. Halliwell's addendum, I see that the both of you are in agreement that one should test for soluble salts contamination ALL THE TIME during surface preparation prior to coatings application procedure. Remember, it is much less costly to test during surface preparation and treat for soluble salts contamination if necessary than to completely redo the entire project within a few short years!

From Michael Halliwell of Thurber Engineering Ltd. on April 3, 2018:
I agree with John and will add that it would be good to test, especially in splash zones, where chloride salts or de-icers (sodium chloride or calcium chloride) are used for snow and ice control (applies to those of use in northern climates).

From John Brodar of Salt River Project on April 2, 2018:
There are at least three situations where I become concerned with soluble salt contamination for exterior atmospheric exposure. These listings are not intended to be all inclusive, merely suggestive. They involve the categories of location, industry and condition. LOCATION: anywhere that experiences fog that originates near the ocean or mining or heavy industry (Visual air pollution is a red flag.). Ocean fog can carry salts inland for 100 miles or more. Mining activities such as acid leach fields or sulfuric acid plants produce airborne contaminants that can be carried long distances by fog. Who knows what contaminants exist in a heavy industry exhaust plume? Cooling towers will carry contaminants in the drift. Anywhere in an identified acid rain problem area is problemmatic. There are national acid rain maps available. Note that nitric acid is also a problem, not just sulfuric. Large flat horizontal surfaces with minimal exposure to rain but windblown dust may be susceptible to salt contamination. INDUSTRY: power generation including flue gas desulfurization; pulp and paper (chlorine and chlorides); sewage and waste treatment (hydrogen sulfide); swimming pools; sulfuric acid plants or utilization; steel making; smelting or refining; oil refineries; any industry using sulfuric acid, chlorine, or dealing with Na Cl (salt); ocean or overseas shipments, Includes deck cargo, hold cargo and container cargo; roadways and bridges subject to de-icing salt; airports/aircraft utilizing de-icing chemicals; rural areas subject to aerial crop spraying, either fertilizers or pesticides. CONDITION: any new steel with unusual rusting, showing dark brown or black rust. Abrasive-blasted steel should remain rust-free for very long periods of time unless liquid water collects on the surface from rain, snow, dew etc. Surfaces kept above the dew point that experience flash rusting ARE CONTAMINATED. If you have made repairs that only last for a year or two even though you “have done everything right,” suspect soluble salt contamination. Today’s maintenance coatings should provide a decade or more of trouble-free service if applied on a decontaminated surface. If you have to repair the same area year after year, suspect soluble ion contamination. In the case of  premature failure of touch-up work or a refresher coat, suspect soluble ion contamination.

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Tagged categories: Salt contaminant levels; Soluble salts; Surface preparation; Surface Preparation


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