In previous blogs about cleaning in the remanufacture environment, we discussed the important first steps in designing a new, more advanced cleaning process. After that, you’ll need to determine how to optimize the interactions between the alloys of the parts, the soils you’re removing and the cleaners that remove them.
Start with Substrate
First, ensure cleaners are compatible with the substrate—the metals and other materials you’re cleaning. Common substrates seen in engine remanufacturing facilities include cast iron, steel, and wrought/cast aluminum.
Cast iron—Used for many engine components, this can very challenging to clean. Cast iron often has a rough surface profile and therefore a higher surface area for soils to be removed from. Cast iron can also be discolored by some cleaners.
Steel—The most robust substrate from a cleaning standpoint, withstands the most aggressive cleaning chemicals, as well as the elevated temperatures and mechanical action required to remove some of the most tenacious soils.
Aluminum Alloys—Depending on the soils involved, aluminum can be a difficult substrate to clean. The aggressive cleaning operations used for ferrous alloys cannot be applied to aluminum alloys without damage to the substrate.
Next, Match Chemistry to Soils
Remanufacturers remove extremely tenacious soils, including oils, greases, burnt on carbonaceous soils, rust, and organic coatings. This may require multiple cleaners applied at multiple stations.
There may also be the need to remove paint from incoming parts, often multiple coats. Be sure to choose a remover that is compatible with your substrate; Aluminum can be damaged by some of the most commonly used aqueous paint removers, most of which were designed for use with ferrous alloys.
Some soils require a special approach. For example, moderate temperatures, spray pressure and stage times will be needed to remove metalworking fluids because of their water-soluble chemistry.
Oil and wax based stamping, drawing and die lubricants present a significant challenge. The chlorinated paraffins commonly found in them may require high performance/highly caustic cleaners or high temperatures to efficiently clean in traditional spray washers. Cleaner formulations designed for lower temperatures will likely need lab testing to validate performance on the substrate.
Welding and brazing residues present a different obstacle because they are difficult to remove and their chemistry is different from other soils. While the best approach to the carbonaceous materials that make up the majority of the soils seen on engines will be an alkaline cleaner, cleaning welding marks requires the use of acidic pickling agents. Getting this right is crucial because welding spots interfere with paint adhesion.
Determine Your Need for Additives
Meeting all the needs of a cleaning process with a single cleaner—removing difficult soils, protecting the substrate, preserving worker safety, saving energy, preventing corrosion, etc.—is a daunting, or even impossible task. Fortunately, additives can help you accomplish goals that otherwise might be out of reach or require more time and expense.
Sequestrants can tie up troublesome metal ions and hard water ions in solution, helping preserve the life of cleaning solutions. Corrosion inhibitors will prevent oxidation, tarnishing and staining in substrates. Oxygenated solvents such as propylene glycol and ethylene glycol ethers will add cleaning power. Foam interferes with pumps, cleaning equipment and spray action, leading to incomplete cleaning. Defoamer additives eliminate those problems.
Refining the Process May Require Help
If you need more information and input to solve the problems of designing a new process, we have just the resource. Download our free white paper, Remanufacture Cleaning—Problems, Solutions and Control, and you’ll have the information to make a successful transition to better technology.