Industrial Surface Chemistry

Guidelines for Choosing a Metal Parts Cleaning Method

Today, most metal fabricators and machine shops have two parts-cleaning options: aqueous water-based cleaning or solvent-based cleaning inside a vapor degreaser. Both methods can provide quality cleaning results. However, each has its distinct drawbacks and advantages.

Aqueous or water cleaning is a process that uses water and chemical additives to get parts clean. The water is treated with detergents or surfactants, builders, emulsifiers, saponifers, sequestering agents, chelating agents and a variety of other compounds to boost the cleaning performance. Using a three-step process, parts are washed in a series of machines, followed by a secondary rinse step to carry away any detergent residue. Then a third step dries the parts using hot air knives or isopropyl alcohol. Aqueous cleaning works with a combination of detergents, high heat and agitation, also known as ultrasonics, to break down soils and remove them from the parts surfaces.

Depending on the reactive additives incorporated into the water, the cleaning agent can be very mild or very strong and can range from nontoxic to dangerous. Some of the additives can be very aggressive on different metals, plastics or inks, so all parts materials must be tested for compatibility prior to cleaning. In addition, the parts should be tested post-cleaning to ensure no reactive material is left behind from the rinse process. After cleaning, the wastewater is filtered, distilled, deionized and osmosis prepped for disposal.

Aqueous cleaning works well and is particularly useful when combining the cleaning process with other procedures, such as depositing rust-preventers and brightener coatings.

Solvent-based cleaning cleans, rinses and dries parts in just one step inside a single machine. Parts are placed inside a vapor-degreasing machine filled with a solvent-based cleaning fluid. Most solvent-based cleaning fluids are a mixture of compounds that can include hydrocarbons such as mineral spirits, isopropanol and ethanol. How the compounds are combined determines the cleaning fluid’s effectiveness and its material compatibility. The vapor degreaser can use just one type of cleaning fluid or can be mixed, blended or custom formulated to remove a specific soil from a specific substrate, maximizing cleaning effectiveness.

Parts are immersed in the continuously filtered and distilled cleaning fluid to dissolve the soils from the parts surface. In some instances, ultrasonic agitation is added for additional cleaning muscle. No additional detergents or additives are needed to dissolve the soils. As the parts are removed from the cleaning fluid, they undergo a brief vapor rinse and drying process. The cleaning fluid condenses and drips back into the vapor degreaser to be reused. The vapor degreaser reuses and recycles the cleaning fluid hundreds of times before it needs to be refreshed or replaced. This helps reduce the cost of hazardous waste removal. The parts come out clean, rinsed, dried and ready for the next stage of production.

Simple Guidelines for Choosing a Metal Parts Cleaning Method

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