How The Pros Coat Their Knife Blades

ESEE knives receive the Textured Powder Coat at Rowen Mfg. (Rowen Mfg. photo)

     A coated blade offers protection, non-glare and striking looks. For those who serve in the military, preserve the peace through law enforcement or knife enthusiasts in general, blades are coated black, Flat Dark Earth, tan or what have you for a variety of reasons, and are permanent fixtures in their complement of working gear. The look and feel are appealing, and the ease of maintenance is an attractive attribute.

     Buying a coated blade makes a statement and serves a practical purpose. Knife manufacturers recognize the demand for such blades and see their contributions to the available selection as filling a necessary niche.

     According to Paul Tsujimoto, senior engineer at KA-BAR Knives, powder coating was developed in the mid-to-late 1960s. “Powder coating is applied using the electrostatic principle,” he said. “The parts to be coated are given a negative charge and the powder coat is given a positive charge and sprayed on. The dry coated parts are then baked in an oven or furnace, where the powder melts and fuses into a hard, protective finish.”

     For ESEE Knives, Rowen Mfg. applies Textured Powder Coat to blades of 1095 carbon steel through an electrostatic spray process that causes powder particles to adhere to the steel. Then the coated steel goes through four stages to complete the process: melt, flow, gel and cure.

     “The powder is applied with an electrostatic spray gun. Before the powder is sent to the gun, it is fluidized to separate the individual grains of powder and improve the electrostatic charge that can be applied to the powder so that the powder flows more easily to the gun. Because the powder particles are electrostatically charged, the powder wraps around the back of the part as it passes by toward the air off-take system,” ESEE’s Jeff Randall explained. “To obtain the final solid, tough, abrasion-resistant coating, the powder-coated items are placed in an oven and heated to temperatures that range from 160 to 210 degrees Celsius, depending on the powder—400 degrees in our case.”

     President and co-owner of Spartan Blades, Curtis Iovito said his company’s coating of knife blades is called Physical Vapor Deposition (PVD). “The process is characterized by the creation of a material vapor that can be reacted with different gases to form a thin film coating,” he noted. “We use a method called arc deposition. This process is carried out under high vacuum conditions. One of the nice properties of PVD coating is that it applies uniformly so that you don’t get build-up on corners and edges like some coatings.” IonBond coats Spartan’s blades.

     The commercial name Spartan Blades has given its PVD coating is SpartaCoat. Iovito and business partner Mark Carey became familiar with PVD coating while working on the development of a new rifle with Special Forces applications.

     “While in the Army, we had been looking for a durable coating in [a Flat Dark Earth color] for a new weapons system we were developing,” Iovito remarked. “Fortunately, we were aware that the development of a true Flat Dark Earth Pantone had been done using zirconium carbon nitride. We believe that we were the first company to use a true Flat Dark Earth PVD coating on knives. This coating is often referred to as diamond-like coating, or DLC, in the gun and knife industry because of its resistance to wear.”

     Black Traction Coating is the proprietary name of the finish TOPS Knives uses on its blades through the services of James Bowen. “We use an epoxy hybrid base with polyester in it,” company President Mike Fuller said. “It is electrostatically applied in its dry powder form, and it goes on the blade between three and five thousandths-inch thickness. The knives are then put into an oven and baked at a little over 400 degrees Fahrenheit for about 17 minutes, depending on the thickness of the material. It’s not an ultra-smooth finish like some coatings have, and it enables the user to hold the blade for close work if necessary.”

Carbon and Stainless

While the processes are similar from manufacturer to manufacturer, each has its own variation on the coating theme. KA-BAR coats both carbon and stainless steels, while ESEE uses 1095 carbon steel exclusively as a blade material. Spartan Blades uses CPM-S30V and S35VN, and 154CM stainless steels.

     “At our clients’ request, we use Black Traction Coating on all our products, 1095, 5160 and all the stainless steels as well,” TOPS’ Fuller noted. “One of the reasons we use it on 440C or 154CM stainless is that it preserves the visual integrity of the blade as well as being easier to clean. It doesn’t add appreciably to the cost of the knife, but the benefit from our perspective is that the chance for oxidation is nil where the covering takes place. However, in areas like the final edge of the knife where there is no covering, the blade still needs to be oiled like any other good tool.”

     Spartan officials acknowledge that the coating of their stainless steels follows the surface blasting of the blades in order to eliminate glare. However, when a knife blade is blasted, a surface is created that is less corrosion resistant. Therefore, the PVD/SpartaCoat helps resist corrosion and maintain the flat finish.

     Tsujimoto identifies four primary reasons for coating knife blades: corrosion protection, anti-reflection, enhancing cutting lubricity, and any combination of the first three. “KA-BAR is no exception,” he said. “Because we use a lot of carbon steel that is very prone to corrosion, we utilize blade coatings a great deal. Stainless is coated for both anti-reflection and corrosion. Remember, stainless steel means that it will stain less than carbon steel. Stainless is not totally stain proof.” Iovito agreed.

     “Knives generally are coated to provide anti-glare surfaces and provide wear resistance, as well as to add additional corrosion resistance, not to mention that it makes for a great looking finish,” Iovito noted. “This finish should not be confused with other spray or paint finishes. While these other finishes are OK, PVD coating cannot chip or rub off because it’s bonded to the steel at a molecular level.”

     Of course, the coating in and of itself is only as good as its ability to stay on the blade. Durability may relate to the composition of the coating itself, and to the degree of abuse and wear a particular knife is expected to weather. Recoating of blades is either rare or not offered by many manufacturers, and the premise is simple. The coating is made to last.

     SpartaCoat is applied at a thickness of 3-to-5 microns, and its final hardness registers 70-to-90 HRC on the Rockwell scale. Spartan has recoated some blades in the past, primarily because the owner requested a change of color or to have something etched on the blade. Iovito said only a couple have been recoated for any other reason through the years.

Snowmobiles & Indian Chiefs

The coating of blades has a practical, aesthetic and utilitarian appeal. It adds an element of safety, stealth, survival and style to a blade, while demonstrating a good value every day in the field. Two of Fuller’s experiences are telling. 

     “Some time ago we were working with a snowmobile manufacturer,” Fuller commented. “The manufacturer used the coating material as an undercoating on its snowmobiles. That says something about the toughness of our Black Traction Coating. It’s extremely durable with a bit of flexibility, and the mixture we make has passed military 24-hour saltwater spray tests and chemical emergent tests with flying colors.

     “Years ago, a survival expert took one of our knives to the Peruvian Amazon and left it with a chief down there. These people use their knives every day and sharpen them on river stones.” The survival expert went back three or four years later, Fuller added, and found the chief, who still had the knife—and the coating on the blade was intact.—By Mike Haskew

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