Aqueous cleaning, meaning cleaning with water versus dry scrubbing, has some key components that make it the most successful. Sometimes people get some of these right, but not focusing enough on others can leave frustrating residue — or leave surfaces that aren’t fully disinfected.
The 6 major aspects of successful aqueous cleaning are these:
- Agitation – types of repetitive movement/friction that loosen dirt
- Chemistry – what types of cleaners are used
- Temperature – washing cold or in high temperatures
- Time – how long are the disinfectants exposed to the area?
- Rinsing – what methods are most appropriate for rinsing the item
- Drying – properly drying the item without damage, and whether heated drying is used to help with disinfection
Agitation
Agitation in aqueous cleaning can be achieved in several ways, depending on the equipment used and the nature of the parts being cleaned. For instance, manual scrubbing is an option when dealing with larger, more robust parts.
However, for delicate, complex, or small parts, or when dealing with high volumes, more automated methods are used.
Immersion cleaning tanks with agitation features are one such method. These tanks use mechanical means such as paddles, air bubbling, or ultrasonic waves to create movement in the cleaning solution. The agitation level can be controlled to provide gentle or vigorous cleaning as required.
Let’s take an example of a machine shop dealing with parts contaminated with heavy grease. An immersion tank with air bubbling agitation could be used. The air bubbles rising through the cleaning solution would provide gentle, yet consistent agitation, helping to loosen and remove the grease from the part surfaces.
Ultrasonic cleaning is another form of agitation that’s effective for very delicate or intricate parts. Ultrasonic cleaners work by creating high-frequency sound waves in the cleaning solution, causing millions of tiny bubbles to form and collapse. This process, known as cavitation, produces a highly effective scrubbing action on a microscopic level, dislodging contaminants even from the smallest crevices and holes.
For example, ultrasonic cleaning could be ideal for cleaning a batch of intricate watch parts. The agitation created by the ultrasonic waves would effectively remove contaminants from every nook and cranny without damaging the delicate components.
Type of Cleaning Chemicals Used
Cleaning agents used in aqueous cleaning can be broadly classified into three categories – alkaline cleaners, acid cleaners, and specialty detergents. Each type serves a unique purpose and comes with its own set of strengths and limitations.
Alkaline cleaners are primarily used for degreasing and are particularly effective in removing organic substances like oils, fats, and proteins. These cleaning agents increase the solubility of these substances, making it easier for the cleaning solution to lift them off the surface.
For instance, in an automotive shop dealing with greasy engine parts, an alkaline cleaner would be the first choice due to its effectiveness against grease and oil.
Acid cleaners, on the other hand, are highly effective in removing inorganic substances such as mineral deposits, rust, and scale. These cleaners work by reacting chemically with the contaminants, loosening them from the surface for easy removal.
For instance, in a water treatment plant dealing with mineral scale build-up in pipes, an acid cleaner could efficiently remove the scale without damaging the pipe material.
Specialty detergents are custom-formulated cleaning agents designed to tackle specific types of contaminants or to be compatible with particular materials. F
or instance, in an electronics manufacturing plant, where standard alkaline or acid cleaners may cause damage, a specially formulated detergent with a neutral pH could be used to safely and effectively clean sensitive components.
Temperature
The temperature of the cleaning solution directly influences the cleaning action. Higher temperatures generally increase the solubility of contaminants, helping to dislodge and dissolve them more effectively.
Additionally, higher temperatures can accelerate the chemical reactions between the cleaning agent and the contaminants, further enhancing the cleaning process.
However, the optimum temperature can vary depending on the cleaning agent used and the nature of the contaminants.
For instance, an alkaline cleaner for removing heavy grease might work best at a higher temperature, whereas a specialty detergent for sensitive electronics might require a lower temperature to prevent damage.
Time
The duration of the cleaning process is another crucial factor. Insufficient cleaning time may not allow the cleaning agent to fully react with the contaminants, leading to inadequate cleaning.
Conversely, overly long cleaning times can be wasteful in terms of energy, time, and cleaning agent usage, and in some cases, can even cause damage to the part.
Balancing the cleaning time involves considering the type of contaminant, the effectiveness of the cleaning agent, and the agitation method used.
For example, a heavily soiled component might require longer immersion time in an agitation tank, while a lightly soiled part could be effectively cleaned with a quick ultrasonic cleaning session.
Rinsing
Rinsing is a crucial step following the cleaning process. It helps to remove any remaining contaminants and cleaning agent residues from the part surface.
Poor rinsing can lead to recontamination, stains, or even potential damage to the part.
The quality of the rinse water can also affect the rinsing effectiveness. In some cases, deionized or distilled water might be used to avoid leaving mineral residues on the part.
For example, in the cleaning of optical components, high-quality rinse water would be essential to prevent water spots and ensure a crystal-clear finish.
Drying
The final stage of the aqueous cleaning process is drying. Proper drying is necessary to prevent water spots, corrosion, or other issues caused by moisture.
The drying method can range from simple air drying to more sophisticated techniques like heated drying, blow-off with compressed air, or even vacuum drying.
The choice of drying method can depend on the part’s material, the nature of the cleaning process, and the desired cleanliness level. For example, a metal part cleaned with an alkaline cleaner might be dried in a heated oven to speed up the drying process and prevent corrosion, while a delicate electronic component might be dried using a gentle blow-off method to avoid thermal stress.