Quaker Chemical Corporation is a leading global provider of industrial lubricants, hydraulic
fluids, drilling fluids and metalworking fluids. They provide approximately 350 different
process fluids and associated services to a wide range of industries including steel, aluminum,
automobile, mining, aerospace, tube and pipe coatings and building materials. Quakers
headquarters are located in Conshohocken, Pennsylvania. Since 1962 the European
headquarters are based in Uithoorn, the Netherlands and from 1963 it has worldwide offices
in England, Italy, Australia, Japan, Spain, South Africa, Mexico and Canada.
Many of the metal working products are emulsifiables. They consist of a lot of different,
typically technical-grade, raw materials. These emulsions are offered as a concentrate to the
customer, and mixed on site with water up to volumes between 1 and 100 m3. The water, used
to emulsify these concentrates, is often not de-mineralized water, but on site available ground, river-, or drinking water. This water is often a source of pollution in the emulsions. To
ensure the quality and functioning of the emulsions for the long period of which they are used
over (often several years), various properties of the emulsions are monitored. Think of daily
pH control, weekly microbe tests and monthly difficult microbe tests and more extensive
analysis including chloride determination. Various techniques are available to determine the
chloride concentration, which vary from gravimetric and potentiometric methods like
titration, to high-tech methods as ion chromatograph, X-ray fluorescence (XRF) or
inductively coupled plasma-mass spectrometry (ICP-MS).
When chloride determination is applied to Quaker
products varying of results are found. The variance
is found between different methods, data from
previous determinations, or data from other
locations. This often leads to unresolved debates
about the conditions of the products and makes the
exact condition of the product unknown, which
can lead to improper maintenance with potentially
adverse consequences for the customer, as can be
seen in figure 1. These consequences can be very
serious, regarding the replacements of entire
systems, corroded or damaged machinery and
claims addressed to Quaker.
Figure 1 Example of corrosion on costumer products
Chloride determination has been an issue for quite some time at Quaker. Most of the time
problems arise from differences between chloride concentrations measured by a costumer
(who often not discloses its analytical methods), the analytical department at Quaker, and
even between methods here. There is no problem in analyzing transparent, low content
samples with the Marcherey-Nagel equipment (photometric water analysis), Most Quaker
products though are non-transparent emulsions, so this method does not work here. The most
used method to determine the chloride concentration at Quaker is titration with AgNO3,. This
because it is a very simple technique that can easily be done at the small labs, available at the
fabric. It is based on the reaction of Cl- with Ag+ titration, is an old method to determine
chloride concentrations and can be influenced by a lot of other components that also react
with silver.
Ion chromatography is also a method that is used to analyze chloride, other ions and almost
any other charged or polar molecule, it works good on different kinds of samples and
especially on water. This method is based on high pressure liquid chromatography (HPLC)
but then with the interaction of ions with material in the stationary phase of a column. So it
would be very suitable to measure the chloride content of Quaker products, even though the
columns for the ion chromatograph are not suited for injecting emulsions.
Another method that can be used to detect chloride is X-ray fluorescence. What happens:
Materials are exposed to short wavelength radiation (X- or gamma rays) to excite some of the
atoms present in the sample. When an electron in the excited atom “falls down” in to a lower
orbital, it emits a photon with the exact energy of the difference in energy of the two orbitals.
This is effect is shown in figure 2. This photon is detected and from this exact energy the
element, emitting this specific energy, can be identified and by the intensity of the photons the
concentration can be measured .
Figure 2 simplified mechanism of XRF