P. O. Box 815
TECHNICAL MEMO #2: Choosing between powder and liquid cleaner/coater formulations.
There are effective cleaner/coater formulations in both powder and liquid form on the market that will handle most soil conditions, metal combinations, and washer configurations commonly encountered. Some of the factors which should be considered when choosing between powder and liquid formulations are discussed below.
Safety and convenience in storing and handling the product are obvious factors, and largely a matter of personal preference. Spills of powder products are more easily contained, cleaned up, and reclaimed than liquid, but it is generally easier to set up a liquid formulation for automatic control and replenishment, if this is desired (see Technical Memo #17: Automated Testing and Control). In storage, liquids are subject to damage from low temperatures, while powders may pack or cake in the drum, particularly after being opened.
Quality levels attainable need not vary between powder and liquid forms of cleaner/coaters, since either form can result in basically the same composition in the operating bath. The following table shows a comparison between two types of formulation, one powder and one liquid, which could result in very similar bath compositions.
|FILLER||SODIUM SULFATE 33-40%||WATER 40-60%|
|COATING AGENT||MONOSODIUM PHOSPHATE 50-60%||PHOSPHORIC ACID 18-25%, SODA ASH 5-12%|
|ACCELERATOR||OXIDIZER 5-10%||OXIDIZER 3-6%|
|CLEANING AGENTS||SURFACTANTS (3) 2-4%||SURFACTANTS (3) 3-6%|
|COUPLING AGENT||N/A||HYDROTROPE 2-12%|
It is generally fair to say that it is easier to produce a "balanced" product in liquid form, and that powder products are more likely to require side additions to increase cleaning or adjust pH. It should also be noted that the "filler" in a liquid product (water) does not contribute to sludge in the work tank as do materials added to powder products as fillers, surfactant carriers, or drying agents.
Salesmen will sometimes say that powders are "100% active" while liquids are necessarily diluted with water. The fact is that powder products usually have a "filler" material added to carry additional surfactant, and to reduce the product's price into the market range. They may say that the amount of surfactant that can be added to a powder product is limited by the need to produce a loose, dry product, while a liquid product can contain much more surfactant. These statements have some truth in them, but some surfactants are available in a dry form, and there are materials that can be added to powders to absorb and carry larger amounts of surfactant without caking in the drum. In liquid products, a "coupling agent" must usually be added to prevent the surfactants from separating in the drum, which adds cost and can cause quality problems under some conditions.
Differences in operating costs are less obvious. Freight costs will be higher for liquid materials because a given operation will normally use about twice as many pounds of liquid as they would powder. Container costs (up to $ .06 per pound) tend to favor powders. However, since liquid cleaner/coaters are usually priced much lower than powders, the final cost of operation is usually very competetive between the two.
In actual practice with our products, we have not found either form of product to have any decisive advantage in quality or cost performance. We generally tend to favor liquid cleaner/coater formulations because of lower sludge and easier bath control.