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Thursday, April 23, 2009

Aqueous Degreaser

Question:
Do you have an aqueous degreaser to replace chlorinated solvents?

Answer:
Chlorinated solvents clean by solvating residues. Many polar organic and inorganic residues are soluble in chlorinated solvents. The solvents are typically used in baths where the residue is dissolved in to the bath; or the solvents are used with rags or wipes where the residue is dissolved and transferred to the rag or wipe; or in some cases the solvents are used in vapor degreasers where the solvent condenses on to the substrate and drips off in to the tank carrying the residue with it. In all cases, you typically keep cleaning to the point where enough residue is removed and you are now left with clean enough solvent on the substrate. In effect, these solvents are self rinsing. Once cleaning and rinsing are completed, then the last of the solvent evaporates away to dryness.

Aqueous cleaners can quite easily be used to remove polar organic and inorganic residues. In fact depending on what cleaner is used, aqueous cleaners can additionally remove particulates, oxides and a range of non-polar and other organic residues that are not soluble in chlorinated solvents. The method of use and cleaning mechanisms for using aqueous cleaners are quite different from solvent cleaning. Aqueous cleaners work by emulsifying, dispersing, wetting, chelating, dissolving, and saponifying residues. The big difference is that aqueous cleaners need to be rinsed with water. Aqueous cleaners also benefit from using heat, whereas for safety reasons, you usually do not heat chlorinated solvents except in vapor degreasers. You typically need to change the cleaning procedures to switch from a chlorinated solvent to an aqueous cleaner.

If you were using soak tanks to clean with chlorinated solvent, you can typically use a soak tank with warm 1% Liquinox followed by a thorough water rinse to get comparable or better cleaning. If you are using a vapor degreaser, typically you would use a warm or hot 1% Liquinox solution in an ultrasonic tank followed by a thorough water rinse to get comparable or better cleaning. If you were using chlorinated solvents with rags, you can often use rags of warm 1% Liquinox to clean with, followed by whatever best rinse is practical using other rinse water rags or ideally a running water rinse. The kinds of residues that are best removed by chlorinated solvents can typically be readily removed by Liquinox.

One other key difference between aqueous cleaners and chlorinated solvents is that the rinse water used can cause rust on certain kinds of tool steel, mild steel and iron. Since Liquinox is a residue-free cleaner, there are no corrosion inhibiting residues that will survive the rinse process. Once the detergent is rinsed away, any dissolved oxygen in the rinse water can attack the steel and cause rust. Typically rusting will not occur during cleaning, but during rinsing. You can minimize and control any rusting by being sure to rinse with cool ambient temperature water and the drying promptly by a water removing process rather than a water evaporating process. Water removing drying processes include wiping, blowing off with air or gas jets, dipping in isopropanol or other drying solvents. On stainless steel, plastics, ceramics and most other substrates there are not corrosion concerns with mild aqueous cleaners like Liquinox.

For more information, please download the LIQUINOX technical bulletin.

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