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Tuesday, September 25, 2007

Aqueous Cleaning Consideration Questions

What are important questions to consider when selecting an aqueous cleaner?

Today's aqueous critical-cleaning detergents are blended for specific applications-substrate, degree of soil load, and cleaning process-these, are all important considerations when selecting a detergent. Here are a few questions to ask about a detergent brand to ensure that it meets your specific cleaning needs:

1. Does it have good detergency on the types of soils that you need to remove? A broad range of organic and inorganic soils are readily removed by mild-alkaline cleaners that contain a blend of surfactants and sequestering agents. Metallic and inorganic soils are often readily solubilized by acid cleaners. Proteinaceous soils are effectively digested by protease enzyme cleaners.

2. Is it free-rinsing? Will it rinse away without leaving interfering detergent residue? A properly formulated detergent will contain rinse aids to help the rinse water remove the detergent and soil solution. Rinsing is a critical part of high-performance cleaning. The detergent usually loosens all the soil from the surface and then the rinse water sweeps it away. Use a non depositing nonionic rinse aid. Many rinse aids are cationic positively charged compounds that are attracted to a surfaces that repel the water, this can leave a surface covered with the water repelling rinse aid.

3. Is the detergent recommended for the desired cleaning method? Use low foam cleaners for high agitation cleaning (pressure spray wash, dishwasher, etc. ). Use high foam cleaners for immersion or soaking (manual, ultrasonic, etc.).

4. How hazardous is it? For example, is it highly alkaline or acidic, presenting a personal health hazard? Is it corrosive? Does it present a reactivity hazard with soils? Is it a flammable or volatile solvent? These considerations can be evaluated by reviewing a Material Safety Data Sheet for the agent. Preferably, it should not contain any hazardous ingredients listed on the OSHA standard and Hazardous Substance List 29CFR 1910 subpart Z.

5. Can it be disposed of easily? Any detergent chosen should be readily disposable and biodegradable, containing no RCRA Hazard Classification or EPA Priority.

6. Is it environmentally friendly? Considerations include ozone depletion potential and volatile organic compound (VOC) content regulated by the Clean Air Act Amendments. Approval under anticipated future restrictions should be weighed as well.

7. How economical is it? The detergent should be widely available and affordable. For optimal economy, a concentrated detergent is typically used at 1:100 dilutions.
In choosing an appropriate detergent, one must consider the equipment being cleaned, the cleaning method, the degree of cleanliness and residue removal that are necessary and the performance of the detergent. Key questions to ask about selecting a cleaner are:

- Does it have fillers? There are a number of ways to tell whether the powder or liquid brand you're considering contains excess fillers or is optimally concentrated.

- What are the ingredients?

Powders: When selecting a powdered brand, look at the label, technical bulletins, and MSDS to see if it contains any sodium chloride or sodium sulfate compounds which do not perform a useful cleaning function but merely add to volume and weight (and shipping costs).

Liquids: With liquid detergents, the most common filler is water. It is important, however, that no more water is used than necessary to ensure a good solution, maintain stability, and prolong shelf life.

- What is the concentration?
Powders: It is rare that a detergent will require more than a 1 percent solution of detergent to water (1:100) for good detergency. For long bath life, in some cases higher concentrations up to 3 or 4 percent are acceptable.

Liquids: Typically, an alkaline cleaner will not require a dilution greater than one percent (1:100). Whereas, a semi aqueous or solvent-containing cleaner may require a dilution of two percent (2:100) or more. Again, for long bath life, higher concentrations are acceptable.

- What are the operating costs? Operating costs for aqueous cleaners are generally low since these cleaners are usually concentrated-typically using only one to five percent of cleaner solution to water. In addition, aqueous cleaning baths last a relatively long time without recycling.

Strong acid cleaners generally require constant system maintenance since their aggressive chemistry can attack tank walls, pump components, and other system parts as well as the materials to be cleaned. (Inhibitors can be used to reduce such attack.) Another disadvantage of strong acid cleaners stems from soil loading-particularly metal loading-which requires frequent decanting and bath dumping, leading to relatively high operating costs compared with alkaline cleaners.
In contrast, alkaline cleaners are often more economical compared to acid chemistries, because they do not cause excessive maintenance problems.

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