Solvent degreasing is the process of applying organic solvents to a material or part to strip away contaminants from the material. By stripping away any contaminants, the material can be further processed via dyeing, painting or electroplating. The three most common ways of performing solvent degreasing are spraying, brushing and immersion, depending on how much solvent is needed to degrease the item. Different degreasing machines are used to apply solvents and are known as cold cleaners, conveyorized degreasers and open-top vapor units. Benefits of using solvents for degreasing include lower resulting emissions and the minimal need for venting; on the flip side, solvents can be a fire hazard, even minimal emissions are still toxic and it can be hard to dispose of the solvents.
When an item such as a tool is being processed, it will collect machining fluid and other substances that are considered contaminants. These fluids keep the item from being processed any further, because the contaminants would interfere with processes such as electroplating or painting. To clean the item, companies use solvent degreasing, in which a solvent degreaser agent is applied directly to the item to strip away all contaminants.
Solvent degreasers are all organic compounds, meaning they have carbon and are based on chlorine, petroleum or alcohol. This is used on many types of metal and plastic items, because the solvents will not affect metal and plastic. The solvent is liquid-based, so it can easily flood or cover the entire part, meaning every section will be degreased and cleaned.
When applying a solvent, the three most common application methods are brushing, spraying and immersion. Brushing and spraying are similar, because the solvent is either brushed or sprayed on the part and a relatively small amount of solvent degreasing fluid is actually used. Immersion uses a large pool of solvent, and the item is dumped into the pool. Pickling is similar to immersion, except the parts undergoing pickling are left in for an extended time to remove deep contaminants.
There are several different machines used to perform solvent degreasing. Cold cleaners apply the solvent cold and are loaded by batch. Open-top vapor cleaners also are batch-loaded, but they clean by heating the solvent and using a solvent vapor. Conveyorized units can use both cold and vapor solvents but are continuously loaded.
The benefits of using solvent degreasing over other degreasing methods is that there are fewer emissions and the venting necessary is minimal, so small outfits can be easily set up. The drawbacks include petroleum-based solvents' status as a fire hazard and the fact that emissions, while minimal, are still toxic and dangerous. There also are many regulations placed on solvent use, and disposal can be difficult.