truth about salt testing: What you need to know
Read this before you start testing
for salt contamination.
On any project, what you do is determined by the
work specifications. Testing for salts on steel should be relatively
straightforward, but many specifications are so poorly written that is
often difficult to determine how to test for salts.
Although the terms "chloride" and
"salts" are often used interchangeably, they are actually very
different. It is important for the inspector to determine the proper tests
based on the project specifications. The wording often makes this
Are you testing for total salts or do you need to
test for chloride or does it require testing for CSN (chloride, sulfate and
Nitrites)? Since there are no US
standards to test for salts, many specifiers come up with their own, often
confusing, verbiage. Occasionally, specifiers will require testing in
accordance with ISO 8502, the only internationally recognized salt
Possible ways to
With some basic project information out of the way, inspectors can start
considering different testing options to see which is best for them. Total
salt testing is the most common method, used around the world, and involves
testing for all salts present.
This is the only way to identify the presence of
all soluble ions that may be on a surface. The most common testing method
for total salts is the Bresle test required by ISO 8502-6 and ISO 8502-9.
Though this does not tell you the specific amount of ions present, for
coated surfaces the ion species is not as important as the number of ions.
Another testing option for total salts is
potassium ferricyanide paper, which change color if salts are present on an
iron surface. When iron interacts with salts, specifically the anion, it
forms free iron (a cation). The Free ion (Fe ++ ) reacts with the papers to
create a Prussian Blue shade.
While this does not quantify the amount of salts
present, the absence of color means no further testing is needed. Because
they only indicate whether salts are present, potassium ferricyanide papers
often used in conjunction with other tests to quantify the salts if found.
"Professionals need to sort out
the facts from the fiction."
Specific ion testing helps users look for a
single ion. This can be helpful when there's a particular ion you're
looking for, but it only finds one half of the salt (the anion). If looking
for the chloride ion, this test will tell you how many chloride ions are
present but won't distinguish between different types of chloride salts.
Also, a chloride test that shows zero chlorides
doesn't mean that there aren't any salts present, just that there are no
salts containing chloride. If inspectors use this test, they need to make
sure they don't make any false assumptions.
Regardless of which salt test is used in the
early stages, the conductivity test provides the most accurate reading of
salts present on a surface and is the only way inspectors can be sure that there
is no salt left after cleaning.
Which cleaners to
Just as there are misconceptions about salt testing, there's also some
dangerous myths out there about how to clean salt off. Acid-based cleaners
may remove salts containing chloride, nitrate or sulfide: in fact, since
acidic cleaning solutions are salts, they can also add more contamination
to the surface than you are removing. This may in turn cause more work
since the acid salts have to be cleaned off after application.
A cleaner such as HoldTight® 102 is nonionic and 100 percent volatile. It adds no
salts when cleaning of existing salts and evaporates when it is done. Once
the surface is dry, you can paint without washing it off.
You don't always need a separate cleaner.
To remove water soluble salts only requires Water. If used correctly, you
may be able to remove soluble salts with water that doesn't contain any
chemical additives. The key to removing these salts with just water is
using high quality water at high pressures, generally 3,000 to 5,000 psi
can help remove soluble salts.
Products we offer
MTest has several options available for effective salt contamination
testing. We have the Bresle
test (TQC-SP- 7310) is
the most used salt test in the world and virtually the only test used in
most countries except north America. We now have the new DeFelsko SST probe
and Posipatch which is an
improved version of the Bresle test.
While I do not believe chloride testing is the
best way to test for salts, occasionally chloride testing is required by
the specifications. For this reason, we offer the CHLOR*TEST which offers
surface, abrasive and water testing kits for chloride, as well as their CSN
Kit. We have just developed our own
Chloride Anion test which utilizes the Posipatch and has the added
advantages of being less expensive and working as both a Chloride test and
Bresle test. We are also developing
a CSN test which we hope to have available latter this year.
For rapid screening, inspectors can purchase a
package of several potassium ferricyanide test papers for just $25. We also
offer the Parks SSM salt meter for fast an easy testing, and have recently
put together a SACK
test kit and SACK TEST L which will test for
salts and/or chloride in abrasives, in the wash water and on the surface of
Reach out to us today for salt tests that are
both affordable and effective. You can read more about salt testing myths
in inthis Blog
have the right tools to test for salt on a steel surface?