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impregnated part. The list is endless," he says. In this location since 1988, the company serves many different markets. Gebhard explains that by resolving the problem of the subsurface porosity, the ultimate result of the surface finishing, whether painting, plating, anodizing and so on, is better and the number of rejects is substantially reduced. In the case of aluminum castings, he says that companies often lose up to 10 and 20 percent of production without impregna- tion. The cost of impregnation is generally less than 5 percent of the cost of the casting itself, so it easily offsets those potential losses from rejected parts. The Need for Clean Of course preparing a part's surface for final finishing opera- tions goes beyond impregnation. Dealing with a variety of manufacturers such as automotive and aerospace, Imtech's cleaning line has delivered on significant demands. About half of the parts that the company processes go through its vapor degreasing system. The more difficult the porosity-associ- ated issue is, whether it's a finishing or a pressure-tightness problem, the more likely it is to be cleaned. According to Gebhard, people don't always realize vapor degreasing is still a viable option, but with the right control processes in place, it can indeed serve as the best option in many applications. "When dealing with the porosity in castings, water-based cleaning has very specific limitations," he says. "You start with water—the cleaning media—and it has a surface tension in the mid-70 dynes. To get it to clean, you have to lower that surface tension with detergents, just like when washing dishes. Adding a surfactant helps to break down the dirt in an electrochemical reaction." But there is still a limitation because even after adding the chemistry to the cleaning water and adding ultrasound energy or impingement energy (a spray), or some sort of washing energy such as tumbling, the surface tension continues to be kind of high, and the water itself cannot enter the pores that it needs to. Oils and other contaminants have a much lower surface tension somewhere in the teens (dynes). "To deal with these contaminants, the perchloroethylene solvent that we use is down around 2 dynes, and when it's at temperature it's below 1," Gebhard explains. "It easily gets into the porosity and displaces the contaminants. Then we take it out through an evaporation process and we have a clean part." The System Imtech has been using a Serec airless vapor degreasing system in its facility since 1998, with a new system being added about two years ago. Gebhard helped develop the original system in 1990 in response to the Clean Air Act. While this legislation did not ban halogenated solvents, it placed strict guidelines on their use. This vapor degreasing system uses the solvents without losing them like the open-top degreasers did. According to Bill McCormick, president at Serec, roughly 80 percent of the systems sold by the company are customized to fit the customers' applications. Such is the case with the system at Imtech, designed for a variety of metals and part sizes. The system is an airless vacuum machine—a closed-loop system with built-in distillation, heated vacuum solvent recovery. It features low emissions and greater than a 97 percent recovery from the waste stream. Processing under vacuum, there is no solvent/air interface. With no air in the chamber, it is able to perform deep cleaning and drying on complex features. Getting it Done Cleaning can be an expensive step in the production process, but it is valuable—a value determined based on the losses that would be incurred without it. Shops that take cleaning seri- ously are the ones that have fewer reject rates and are the top performers in the industry. Gebhard says, "You can tell when you walk in the doors, by the way a shop is set up and the way they work, that they are serious about cleanliness. These are the shops that will be in business down the road." One Imtech customer had been struggling with a cast titanium ring with an interior diamond coating. Experiencing multiple failures with the part, the company thought impreg- nation may be the solution. By running UV light inspections, Imtech determined that these parts, worth thousands of dollars and previously thought to be "cleanroom quality," had finger- prints on the coatings. While impregnation was useful for these parts, the real impact was the addition of proper cleaning, which is critical for the success of the parts. "Anyone having adhesion problems should first look at their cleaning proce- dures," says Gebhard. "If the material surface is not prepared appropriately, they'll never have success. It's an old issue, but people still don't pay enough attention to it." For more information from Serec Corp., call 401-667-7370 or visit serec-corp.com. PRODUCTS FINISHING — pfonline.com 31 PARTS CLEANING