Porosity sealing is a critical step in parts manufacturing. Porosity refers to any void or hole that forms in the metal during the casting process. A small amount of porosity is almost always present in castings due to various conditions that occur as metal is injected or cooled. Excess porosity can affect a part’s structural integrity and make the part more susceptible to corrosion. In parts intended to hold pressure — such as valves, pumps and compressors — porosity can also create leak paths and render the part unusable.

To protect casting integrity, a sealant is typically applied to die castings and permanent mold castings using a process called vacuum impregnation. In this process, porosity sealants impregnate the material, eliminating leak paths and weaknesses caused by microscopic voids in the material. For this sealing process to be effective, the parts must be spotlessly clean. Any residual contaminants still present from the casting and/or machining processes can compromise the seal and cause the part to fail.

Why Vapor Degreasing Is the Most Effective Way to Clean Castings

Vapor degreasing is widely regarded as the preferred cleaning method for metal castings for a variety of reasons:

• Effective: Vapor degreasing is highly effective at removing oil, grease and contaminants — leaving parts spotlessly clean, dry and ready for sealing.
• Environmentally responsible: Vapor degreasing solvent is used over and over, so little to no chemical is released into the environment during operation. It works well with low-impact solvents, and is very energy-efficient.
• Cost-effective: The efficient use of solvent and energy — along with the speed and simplicity of the procedure — helps keep operation and labor costs contained.
• Space-efficient: Because vapor degreasing does not require separate chambers for cleaning and drying, the equipment takes little space in the shop.
• Easy: The vapor degreasing process is simple, requiring minimal labor and training

How Does Vapor Degreasing Work?

In vapor degreasing, solvent is boiled in a sump to create a vapor, which is contained in the unit by means of chilling coils at the top. This cold area forms a “cold barrier” that causes the solvent to return to liquid form and precipitate back down into the sump. As parts are lowered into the vapor layer, solvent condenses on them and runs off, carrying oil and contaminants with it.

After a few minutes in the vapor atmosphere, the parts can also be lowered into the liquid layer of the sump bath for additional cleaning effect. At the end of the cleaning cycle, the parts are lifted back out of the vapor bath. As they pass through the cold layer, the solvent quickly evaporates, leaving the parts clean and dry.

Where exceptional cleanliness is required, parts may be subjected to a final cleaning cycle — a dip into an adjacent rinse sump filled with solvent; spray cleaning with additional solvent; or ultrasonic cleaning. This ensures that any remaining contaminants are thoroughly removed in preparation for the sealing process.

Effective and Budget-Friendly Casting Cleanliness

While there are other casting cleaning methods available, most parts manufacturers prefer vapor degreasing for its significant benefits over the alternatives. For example, aqueous cleaning systems tend to be slower, more complex and more expensive to operate.

Vapor degreasing also accomplishes cleaning with little to no risk of abrading or damaging parts. If you are looking for a proven effective way to keep your castings clean and ensure high-quality results, give vapor degreasing a try.