Are you getting the best possible melt yields out of your scrap metal? In nonferrous metal recycling operations, the volume of metal you put into your furnace rarely matches the amount you recover. Contaminants such as dirt, fine debris, and coatings add volume to your scrap but offer zero value—and can even contaminate the end product with dross—on returns. When heated, organic material burns off or volatilizes, leaving behind ash that contributes to furnace waste, while nonmetallic contaminants such as sand and debris merge with oxides to form dross. Dross must be skimmed off the final melted product, reducing melt yields and financial returns.
Polishing and cleaning scrap metal before melting it removes contaminants and reduces the chances of oxidation and surface damage, increasing melt yields. Therefore, before loading metals into the furnace, they should be cleaned and decontaminated.
What are the Benefits of Scrap Polishing?
Nonferrous metals, like copper or aluminum, oxidize over time if the polishing and melting process takes too long—especially in hot, humid, or dirty environments. After shredding, metal surface condition can vary greatly, so any surface contaminant, such as dirt or oxidation, results in dross in the output. Dross must be manually removed or disposed of, lowering melt yields and returns on metals, and lowering profits. With proper polishing equipment that can clean and polish large quantities of metal in a short period, such as a polishing drum, you minimize the dross put into your melts. The metal also looks more aesthetically pleasing once polished and cleaned.
Polishing metal also benefits your downstream equipment. For example, contaminants can degrade a furnace’s refractory lining over time. Clean metal also melts faster since it doesn’t have to burn through organics, debris, paint, etc. This reduces energy consumption and cuts operational costs.
Cleaning Methods
After shredding, cleaning and polishing metals helps streamline the process and reduce waste. You can handle this with manual polishing for minor contaminants, or automatically with specialized equipment or chemical treatment.
The primary methods include:
Mechanical cleaning techniques for shaking off loose soil, coatings, and corrosion without needing water or harsh chemicals. These include rotary metal polishers, vibratory screening, abrasive polishing, and shearing. With rotary and vibratory techniques, metal-on-metal tumbling or friction knocks off oxidation and dirt without water. This makes it safer than water-based cleaning methods, since moisture in furnaces is a safety hazard and can cause steam explosions.
Washing and degreasing methods are especially effective for removing mud, grease, and machining fluids. Techniques include spray washing, detergent/alkaline washing, solvent degreasing, and ultrasonic cleaning. The main drawback is that the metal must be completely dry before being sent for melting; moisture in furnaces is an explosion hazard.
Thermal pre-treatment burns off organics and coatings. This technique is excellent for painted or lacquered aluminum, such as aluminum beverage cans or auto shred residue, which has heavy paints, lacquers, and oils. Decoating, thermal de-oiling, and pyrolytic treatment are common methods.
Know the ROI/demand
Uncleaned, mixed scrap melt is worth less than properly cleaned and sorted scrap metal. Therefore, before melting, it’s ideal to separate your nonferrous metals—usually using sorting equipment such as a screen or density separator.
If you need to store polished scrap metal short- or long-term to sell when prices are higher, it’s significantly less prone to oxidation and corrosion than unpolished scrap. Because the dirt, salts, and moisture-trapping debris have been removed, the clean metal can be stored longer without degrading before it’s ready to sell.
Additionally, dross must be disposed of after being removed from the melt. As a result, you’ll have to wait for the dross to cool (which may require additional equipment or labor) and pay disposal fees.
Increase Melt Yield with General Kinematics
General Kinematics’ scrap polishing equipment, such as the Scrap Metal Polishing Drum, and turnkey scrap recycling systems are designed to maximize your material returns and uptime. Whether you need a new solution or want to optimize your current process, contact GK today to get started!
