"Ten years ago, when there wasn’t that much aluminum, people were scared," said Mike Wigert, sales manager of spraywasher manufacturer LS Industries. "They didn’t know how to regulate their ovens, they didn’t know which chemicals to use, and they were tarnishing their aluminum parts, and probably ended up hand cleaning a lot of them," he said.
Cleaning used automotive parts was a lot more straightforward back in the days when cast iron parts were the rule rather than the exception. Aside from the fact that petroleum-based solvents were the cleaning fluids of choice, engine bearings were softer and the oil was thicker. So while cleaning up an engine block or cylinder head prior to using it as a rebuilt engine component was important, it didn’t take on the critical aspect that it does today.
"Engine tolerances and clearances between bearings, pistons and cylinder walls is way less today, and it’s an absolute death knell for an engine to have dirt in it," said Lyle Haley, sales manager at Peterson Machine Tool in Shawnee Mission, KS. Dick Schaffner, owner of Aluminum Head Services in Belton, MO, puts an historical perspective on it. "In the 1940s, they didn’t even put oil filters on cars; look at where engine technology is today," he commented.
Although there are some interesting new methods being tried – bio-remediation comes to mind – the basic technology that the great majority of rebuilders use to clean parts, which are increasingly aluminum, still centers around heating, washing and blasting. Shops we talked to are all over the map about which combination of these three they use. Not surprisingly, the manufacturers of the machines that heat, spray and blast aluminum parts are also all over the map about why their methods are superior.
Cleaning aluminum parts is more time consuming on several levels. John Edie, a service technician at oven maker Winona Van Norman of Black River Falls, WI, pointed out that a cast iron version of a part can be cleaned in a 650°-700° F oven in a period of 20 to 30 minutes, whereas the same part in aluminum needs four to five hours at 350°-400° F.
But a comparatively longer time in the oven is not the only consideration. Peterson Machine Tool makes both spray washers and parts ovens. "I’m a strong advocate of heat cleaning aluminum, even though it takes longer to do it because you can’t use higher temperatures," Peterson’s Lyle Haley said. "Our experience is that you can safely clean aluminum in 500° F, but beyond that, you’re going to soften or anneal it," He also acknowledged that the time factor to heat clean aluminum is seen by some as a problem.
"Thermal cleaning, if you do it properly, isn’t really quick. But even though a cylinder head, for example, may spend more time in a rebuilder’s place of business, thermal cleaning reduces the number of man hours needed to get it clean," he observed, referring to the labor involved in loading and unloading parts from a spray washer and/or a glass beading machine.
Ric Havel, a consultant to Sunnen Products Company, acts as a spokesperson for Sunnen’s line of metal cleaning machines, which run the gamut from spray washers to ovens to airless blasters. But Havel favors thermal cleaning followed by airless blasting, as the preferred way to go for several reasons, one of them being energy efficiency. "An oven takes the primary source of energy, whether that be electric, natural gas, L.P. or fuel oil, and applies it directly to the cleaning job," he pointed out. Other machines take the energy constituents and utilize them to heat a liquid that’s being driven by an electric pump, where the liquid loses it’s heat within moments after it’s sprayed, and needs to constantly draw more energy to keep it hot."
Thermal cleaning alone is not common, primarily because its function is to drive the liquids out of the oils and greases that are on used automobile components. What’s left is usually easy to knock off through some mechanical means. Depending on what the part is, this takes the form of spray washing, and/or blasting with glass beads, plastic beads or steel shot. Occasionally all three methods – heating, washing and blasting, are employed.
Some rebuilders, like Grooms Engines of Nashville, TN, skip the spray wash cleaning sequence altogether. "We bake our aluminum components in an oven at 440° F for eight hours. Then we glass bead them in a "pressure pot" type of beading cabinet, which gives them a very saleable look," said Groom’s vice president, Doug Anderson. "But no washing," he said. "We used to put them in a jet spray booth with a silicone-based soap before glass beading the parts, but we found that doing that just increased the chance of trapping glass beads."
Anderson later said that he does use a spray washer on aluminum parts as a final rinse, but spray washing is not a part of the heavy-duty cleaning process. He feels that the effectiveness of the "pressure pot" type of glass bead machine (as opposed to machines that siphon the beads into the air stream) is a large part of the reason his company has been able to bypass a spray wash cleaning cycle for aluminum parts. "The siphon technology uses a considerable amount of air to create the siphon, so the impact of the glass bead on the part is reduced accordingly," he said. "The net result is that with a pressure pot type of machine, you can clean a head in about half the time."
Aluminum parts are more typically blasted with glass beads or plastic beads than with some other metal. But like everything else in this business, hard and fast rules don’t apply, and there are always manufacturers or users promoting products that overcome the common obstacles.
Sunnen Products’ Havel, for example, pointed out that Sunnen has gone to great lengths to develop a steel media that’s aggressive enough to clean iron, but not overly aggressive to the point that it harms aluminum. He calls it the most copied media in the industry, and claims that its service life is superior to other blast media.
"It’s a stainless steel media, but unlike stainless steel shot or cast steel, which is created through a refractory process, our stainless media is cut on a diagonal from wrought stainless wire," explained Havel. "Wrought stainless has no porosity, so it won’t trap oxide from the iron parts, which can cross-contaminate the aluminum parts," he said. "What’s more, it’s not brittle, so it doesn’t break down as fast. It gives the shop years of useful life, rather than months, without reclamation."
For those that do make spray washers a part of their aluminum parts washing strategy, one question that often comes up is whether to use a different wash solution on aluminum than is used with cast iron.
It’s almost a given that the old petroleum-based solvents are on their way out of most shops, if they haven’t already been banned from the premises. Instead, an aqueous or water-based solution is added to water. A typical concentration would be four to 12-ounces of a chemical mixture per gallon of water to make the water more effective in breaking down petroleum residue, flushing out complex cavities and, in general, cleaning more effectively.
In the not so distant past, when just about everything that got loaded into a spray washer was ferrous, the chemicals added to the water contained a strong concentration of caustic soda, with a pH of around 13.5. But that’s had to change with the increasing use of aluminum parts, which the caustic soda tends to etch and corrode. Consequently, one of the biggest pitfalls in cleaning aluminum is making sure the chemical formulation you’re using is "aluminum safe."
A spokesman for Memphis-based International Chemical Corporation, a manufacturer of chemical formulations used in spray washers, reported that very few shops opt to have two separate cleaning systems – one for aluminum and one for iron and steel parts – although that would seem to be a more efficient strategy. Most of his customers, he said, use dual-purpose cleaners that work reasonably well on cast iron, and do a good job on aluminum. To overcome some of the drawbacks inherent in using a less aggressive chemical on aluminum parts, some spray washer cabinet makers, such as AXE Equipment in Council Grove, KS, urge their customers to begin by soaking parts in the spry wash liquid before loading them into the spray wash cabinet.
International Chemical Company, often referred to as "Interchem" does make some formulations that are designed for cast iron and steel parts only. They’re relatively heavy in the caustic soda department, where the recommended ratio of water to chemicals is eight to 12 ounces per gallon. But Interchem’s dual-purpose formulations for use on aluminum parts are more popular, and most shops clean their iron and steel parts with the same solutions. They contain no caustics and they have additional surfactants that lower the surface tension of water and allow it to penetrate burned on carbon and soils on aluminum when used in concentrations of four to eight ounces per gallon.
One change in the way aluminum must be cleaned is believed to be a result of the design changes in automotive components as much as anything else. "The old cast iron parts didn’t have as many complex cavities," pointed out Jay Miller, a member of the industrial sales staff at A.R.E. Manufacturing Co., one of several cleaning equipment manufacturers in Wichita, KS. "There’s a lot more remote areas, such as the oil galley ways that run down the length of a lot of aluminum heads," he said. "Areas like that are excluded from contact with the hot water solution."
The technology of spray washers is pretty basic, and many of them operate pretty much the same way. There has long been disagreement about whether water pressure is more important than water volume. Most cabinet type spray washers have nozzles of some kind, and shoot the water at the parts at a pressure at the nozzles of between 50 and 75 psi. But any rule of thumb having to do with pressure is hard to establish. "The more nozzles you have and the closer they are to the part, the more efficient cleaning you’ll achieve," pointed out Chris Winslow, sales manager for spray equipment manufacturer Viking Corporation.
The heat of the water/additive solution is usually between 160° and 180° F; the idea being that it needs to be kept under 200° F to prevent any possibility that it starts to boil and bring about pump cavitation. Another concern associated with the use of elevated temperatures has to do with the evaporation rate. Doug Winnefield, a product manager with Hotsy Corporation of Englewood, CO, a parts cleaning manufacturer, pointed out that evaporation rates for most spray washers runs between five and 20% a day, and the hotter the water is, the faster it will evaporate.
Of course, there is a correlation between temperature of the spray liquid and its effectiveness. "We used to design our washers for 180° F tops, but we’ve jumped our machines to operate at 193° F because you really have to have higher temperatures to cut that grease," said A.R.E. Manufacturing’s Miller.
One well-known spray washer manufacturer, G & F Disa/Goff of Seminole, OK, favors high volume. "We don’t use high pressure pumps; we use high volume pumps. Plus, we have a patented process of ‘throwing’ the water at the parts," said David Zehren, a Goff product manager. "This way we maintain a larger droplet size. A droplet transfers a lot more energy to knock off the deposit than water that’s been forced through a nozzle," he pointed out.
Another selling point of his machines, explained Zehren, is that the Goff machines are designed to be used with water alone. "We do add some rust inhibitor when cleaning cast iron, but the strength of our systems is that by not using detergents, the water doesn’t get saturated with the grease and oils in the detergents. We can skim the water to remove the oils and other wastes, and re-use the water continuously," he said.
There are several new technologies being tried. Many rebuilding shops use ultrasonic cleaning. It’s not a new technology – the aerospace, medical and optical industries have used it to clean parts for decades. Over the past few years, however, some companies that make ultrasonic cleaning machines have become more and more interested in serving the heavier industries, such as automotive.
One such company is CAE Ultrasonics of Jamestown, NY. This is a 50-year-old firm that launched its "Grease Monkey Division" in April, 1999 to expand the use of its products by the automotive industry.
"I love aluminum," said CAE Ultrasonics Grease Monkey Division product manager Dick Davis. "They’re the easiest parts for me to clean."
Davis explains that an ultrasonic cleaning machine works in conjunction with water in a 90/10 ratio with a rust inhibitor that’s added before the solution is heated to 130° to 150° F. "So we’re applying heat, ultrasound and liquid, plus in some cases, agitation, too," Davis said. When asked to explain how ultrasonics works to clean parts, Davis said, "the ultrasound transducers create very small cavitation bubbles which implode inward on themselves rather than exploding outward," he explained. "This creates a very fierce explosive force of 10 to 20-thousand psi, but it’s highly localized."
Speed is the real attraction of ultrasonics. "We can clean 95% of your transmission parts in seven to 10 minutes, and most other automotive parts can be cleaned in about 10 minutes," Davis said, adding that in order to achieve maximum effectiveness, parts must be positioned so that they’re exposed to the liquid. "If liquid can surround it, ultrasonics will clean it." Besides speed, Davis pointed out that CAE Grease Monkey ultrasonic machines are highly automated. "People can drop the parts into the machine and go do something else, so it increases productivity, too," he added.
One of the most appealing cleaning technologies, from an environmental standpoint, is what’s known as bio-remediation. This involves adding microbes or enzymes to the spray or soak tank, which actually eat the oil and grease off of the parts. Think of it – no heat, no chemicals, and hardly any waste – just mother nature at work. "Some companies in Europe use it a lot, and they said that after many years of running the bio-remediation machines, instead of gallons and drums of waste to dispose of, they’re down to baggies," commented Wigert of LS Industries.
We spoke to one production rebuilder who has experimented with several of the new cleaning technologies. Dick Gentry, production manager of A.E.R. Manufacturing in Carrolton, TX, said he tried bio-remediation. "It works extremely well, but it’s slow, and it’s not cheap," he said. "When you balance the cost and time, the only place where we had any success with bio-remediation was on rack-and-pinion valve bodies," he said, adding that, "I’m not using it now."
Gentry also tried a new technique involving the use of baking soda to clean aluminum parts. "It worked ok," he said, "but we had problems with its being a ‘one-pass’ material. Ever open to considering a better way, Gentry has also looked at ultrasonic cleaning equipment. "It’s very expensive and we experienced problems with using it to clean auto parts because any oil in the water serves as a damper to the ultrasonic activity," he pointed out. Gentry admitted, however, that "the cleaning action is terrific."
Gentry, along with at least one other rebuilder we talked to, is excited about the possibilities of a new spray wash system that flies in the face of conventional wisdom about the practicality of high pressure spray washing. Those who have seen the results of the CBT-150 spray washer from Jet Pro, a Pierce City, MO, manufacturer, expressed the opinion that the machine represents something really different in terms of speed, quality and low-cost operation.
Jet-Pro engineer and designer Ray Butler, said that his machine, which has been under development for three-and-a half years, is an aqueous washer that’s different from others in that it uses a combination of high pressure and highly engineered nozzles, electronic controls and fixturing. He wouldn’t say much more than that, except to add that it also has an advanced oil separation system and oil skimmer that extracts the waste out of the water so well that the water never needs to be changed. "The oil that pours out of the back of the machine is literally black oil," he said.
Dick Gentry of A.E.R. is very interested. "The high pressure wash system at Jet Pro is a 3000 psi machine, and I’m hoping it will replace the current cleaning system that we use now," he said.
Rebuilders and equipment manufacturers alike expressed the thought that the cosmetic appearance of aluminum parts is critical. "As A.R.E.’s Miller put it, "If you have two entities that are performing the same task, and one is brighter and shiner than the other, and there’s no cost difference, which one will somebody buy?"
There’s an old saying that the packaging of some products is more important than how they function, and perhaps that’s true to some extent in the clean up of aluminum parts. "It’s always perceived that the inside looks like the outside, so the appearance is very important to people," concluded Chris Winslow of Viking Corporation.
