Alternatives to Halogenated Cleaning
January 1, 1996 is the deadline for companies to find alternatives to Class I ozone-depleting chemicals. Many of these chemicals are commonly used cleaning solvents, such as Freon and 1,1,1-trichloroethane. Many companies in Georgia have already begun the transition to non-halogenated solvent alternatives; however, a number have not. Several large manufacturers have stopped producing ozone-depleting chemicals. Production capacity for alternatives may not be adequate to meet demand for companies that procrastinate until the 1996 deadline.
As a result of the phase-out and the increasingly restrictive requirements on the use of ozone-depleting chemicals, both costs and reporting requirements are increasing. For example, all products made after May 15, 1993 with Class I ozone-depleting chemicals must have warning labels describing their effects on the environment. To further complicate the situation, there is no “drop-in” replacement for these widely used compounds at this time, and those technologies that are available may require equipment or process changes. The use of non-ozone depleting hydrocarbon solvents may seem like an easy alternative; however, some of them are under regulatory attack.
This fact sheet will provide a general overview of the options available to meet equipment and parts cleaning needs. Cleaners can generally be broken down into four groups: aqueous cleaners, semi-aqueous cleaners, solvents, and mechanical cleaners.
AQUEOUS CLEANERS
Aqueous cleaners are water-based cleaners that are usually an acid, an alkaline, or are neutral. They are generally the most frequently used alternatives to ozone-depleting solvents. They may range from pure water to various combinations of water, detergents, saponifiers, surfactants, and corrosion inhibitors. Some benefits of aqueous cleaners are lower costs, improved environmental safety, and ease of disposal.
Aqueous cleaning methods include soaking, agitation or turbulence, spraying, or ultrasonics. The method used is determined by the type of soils and substrates on the parts. Soils are classified as organic (e.g. greases and waxes), water soluble inorganic salts (e.g. chlorides) and inert particulates (e.g. dirt and metal fines). Substrates are another important factor to consider in choosing an aqueous cleaner, since acid and alkaline cleaners may attack metal parts. In many cases, additives are placed in aqueous cleaners to minimize these adverse effects. Other disadvantages resulting from a changeover to aqueous cleaners may be equipment or process changes, increased wastewater discharges, and longer drying times.
SEMI-AQUEOUS CLEANERS
Semi-aqueous cleaners can be a mixture of water and hydrocarbons, which require both a rinsing and drying step in the cleaning process. Common semi-aqueous cleaners include terpenes and other hydrocarbons. Terpenes are derived from citrus peels or pine bark, and are common ingredients in various household cleaners and deodorizers. They are effective in removing flux from printed circuit boards and other similar operations. They are generally recyclable, are biodegradable, and effluents may have fuel value. The disadvantages of using a terpine include a low flash point, high initial equipment costs, may require a modification to the wastewater discharge permit due to increased oxygen demand, and could cause adverse respiratory effects in sensitive individuals. Some closed-loop cleaning systems are available to lessen these negative effects.
Hydrocarbon solvents included in this category include petroleum solvents (e.g. mineral spirits and kerosene), and alcohols (e.g. ethanol, isopropanol, and glycol esters), and ketones (e.g. methyl ethyl ketone and acetone). These are effective in removing waxes, oils, and greases, and can be used in cold immersion cleaning or wipe cleaning. They are compatible with most substrates and can be easily recycled. Their disadvantages include low flash points, increased drying times, and many ketones are regulated as ozone precursors.
CHLORINATED SOLVENTS
Chlorinated solvents that are not Class I ozone-depleting chemicals include perchloroethylene, trichloroethylene, and methylene chloride. They are proven cleaners with rapid evaporation rates, low volatile organic compound emissions, and can be easily recycled. Their primary disadvantages are their toxicity and liability concerns. As a result, their use and disposal are heavily regulated. Use of these hydrocarbons as cleaners should only be considered an interim solution.
MECHANICAL CLEANERS
Processes requiring scale or corrosion removal, paint stripping, or carbon removal from metal surfaces can benefit from the use of mechanical cleaners such as sand, beads, baking soda, and frozen carbon dioxide (CO2). They have the advantage of being environmentally safe, are easily disposed, or require no disposal (e.g. CO2). Mechanical cleaners are generally not effective for removing particulates, oils or greases; they are noisy, and have limited use on parts with irregular shapes and crevices.
THE NEXT STEP…
1) Evaluate your current process to determine substrates to be cleaned, soils to be removed, the level of cleanliness needed, and why the parts are dirty.
2) Evaluate your cleaning requirements to eliminate unnecessary steps, change cleaning specifications if possible, and simplify cleaning by limiting the variety of oils and lubricants used at your facility.
3) Evaluate and rank alternative cleaning options available. Factors to be considered in the evaluation include current and future regulatory, permitting and waste management requirements, environmental and health-related issues, and obviously cleaning effectiveness.
4) Call P2AD for free technical assistance on finding solvent alternatives.
The Pollution Prevention Assistance Division (P2AD) is available to help Georgia companies reduce waste and increase profits through pollution prevention. Services range from telephone assistance to on-site evaluations and consultations. The service is free, confidential, and non-regulatory.