Using Boric Acid as a Safe Lubricant for Cold-Forming Processes

Forming lightweight aluminum- or magnesium-based alloys into automotive body parts is very difficult, mainly because of the high friction of the alloy surfaces, the extreme pressures required for metal-working operations, and the inability of conventional lubricants to prevent wear under such stringent conditions.

Most conventional lubricants are flammable and contain chlorine, phosphorus, and sulfur-bearing additives that are potentially hazardous. Removal from finished products and post-treatment/ disposal of these lubricants are difficult and costly.

Argonne scientists discovered that the exceptionally low friction coefficient (0.03-0.05) of boric acid allows deformation of the aluminum- and magnesium-based alloys at relatively low pressures and prevents them from sticking or transferring to the die or roll surfaces. Because it is water-soluble, boric acid can be removed relatively easily from the surfaces of finished products.

When used as a lubricant, boric acid outperforms competing products, costs less, and is abundant, nontoxic, and environmentally safe. It offers the following advantages:

• A clean and cost-effective lubrication technology for aluminum-forming operations
• Lower application and stripping/removal costs
• Elimination of flammable and hazardous chemicals used as lubricants in current metal-working operations
• Near-perfect finished products that don't require secondary machining or grinding steps (which normally increase the unit costs)

The lubricating mechanism of boric acid is controlled by its special structure.The compound is crystallized in layers in which the atoms are tightly bonded to each other. The layers themselves are weakly bonded; when stressed, they shear and slide over one another easily, so friction is low. The strong bonding between the layers prevents direct contact between sliding parts, minimizing wear.

Argonne is currently demonstrating the self-replenishing nature of boric acid on boron-containing surfaces, the ultra-low friction and wear of grease and oil products containing boric acid, and the ultra-low friction of aluminum surfaces lubricated with boric acid.

Recent laboratory studies have revealed that boric acid has a tendency to form on the naturally oxidized surfaces of aluminum and titanium alloys. This observation could lead to the development of an effective boundary lubricant for cold- forming aluminum and its alloys. Argonne plans to

• Identify and further assess lubrication problems in aluminum-forming operations
• Coordinate effort with interested aluminum manufacturers
• Develop a series of lubricant formulations and test them under shear and stress conditions typical of cold-forming operations
• In collaboration with an industrial partner, perform tests using actual dies and rolls
• Further improve lubricant performance, if required
• Scale up operation and transfer technology for large-scale industrial use