Penephite®, Kroil Penetrant with Graphite

Penephite is Kroil Penetrant with Graphite—it combines Kroil’s penetrating formula with dry graphite lubricant for applications requiring extreme-temperature or high-load lubrication after penetration. Graphite remains stable at temperatures where oil-based lubricants break down, making Penephite the correct choice for applications involving high heat (exhaust components, furnace hardware, industrial ovens) or very high loads (press-fit components, heavy equipment pivot points). Kroil Original is preferred for general penetration; Penephite is preferred when the freed component will continue to operate under conditions that degrade conventional lubricants.

Kroil is a petroleum-based penetrating oil manufactured by Kano Laboratories. It is formulated to creep into the microscopic gaps between corroded or seized metal parts and break the corrosion bond holding them together. It is used primarily to free rusted bolts, nuts, fittings, and frozen mechanical components in automotive, industrial, aviation, agricultural, utilities, and home maintenance applications. Kroil has been manufactured in Nashville, Tennessee since 1950 and is trusted by maintenance professionals, mechanics, and tradespeople across more than a dozen industries.

For most applications, Kroil begins to penetrate within 15 to 30 minutes of application. For heavily corroded or deeply seized parts, allowing Kroil to soak for several hours—or overnight—significantly improves results. A second application after the first soak can further loosen stubborn fasteners. Penetration time depends on the severity of corrosion, the material being treated, and the amount of Kroil applied. In customer reviews, many users report freeing parts that had been stuck for decades, after an extended soak with Kroil.

Kroil Original Penetrant is safe for use on steel, iron, aluminum, brass, copper, and most metal alloys. It is generally safe on most plastics and painted surfaces when used as directed, though prolonged contact with certain plastics or rubber compounds may cause softening or swelling. For applications involving rubber seals, plastic components, or food-contact surfaces, Kroil Clear Food Grade Penetrating Oil (NSF-H1 certified) or Silikroil (Kroil with silicone) are the recommended alternatives. Always refer to the product Safety Data Sheet for material compatibility guidance.

Kroil products should be used in well-ventilated areas. The aerosol formulation produces fine mist particles that should not be inhaled; use outdoors or in spaces with strong airflow when possible. Kroil Original liquid penetrant has a lower vapor pressure than the aerosol and is suitable for controlled indoor shop environments with adequate ventilation. Keep away from open flames, sparks, and high heat sources, as Kroil is a petroleum-based product. Full safety guidance is available in the Kroil Safety Data Sheet at kroil.com/resources/datasheets/.

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Yes, Kroil penetrants are safe and effective on all metals.

Apply Kroil directly to the rusted bolt, nut, or fitting, making sure the product contacts the threads and any visible corrosion. Allow 15 to 30 minutes for initial penetration. For bolts that have been corroded for an extended period, apply a second coat and allow several hours or overnight before attempting removal. After soaking, apply steady rotational pressure with the appropriate wrench or socket—avoid sudden impact until the fastener begins to move. For very stubborn fasteners, alternating tightening and loosening with the wrench (“working” the fastener) while Kroil is still wet often breaks the bond completely. Repeat applications as needed.

Kroil Original Penetrant is widely regarded by professional mechanics and maintenance technicians as one of the most effective penetrating oils for freeing rusted bolts and seized fasteners. Its low surface tension and molecular penetration capability allow it to reach corrosion that lighter penetrants cannot. For exhaust bolts, suspension hardware, and heavily corroded automotive fasteners, Kroil’s extended dwell time formulation provides consistent results. Over 700 verified customer reviews specifically reference freeing rusted bolts and fasteners, many describing success on parts that had been stuck for 10, 20, or 30+ years.

Yes, Kroil products are available to Amazon customers through our authorized reseller, Pattern Products. We also encourage you to shop from a Kroil distributor in your area. Visit our where to buy page for a full listing, and check back often, as new distributors are frequently added.

Yes. Kroil is specifically formulated for heavily corroded fasteners, including those that have been rusted in place for years or decades. Customer reviews document successful removal of bolts and fittings corroded for 20, 30, and in some cases more than 50 years. Extended dwell time is the key variable—for severe corrosion, multiple applications over 12 to 24 hours produce significantly better results than a short soak. In extreme cases, applying Kroil and leaving it overnight, then applying a second coat in the morning before attempting removal, is the recommended approach. To remove rust from metal parts, use Exrust. To proactively prevent rust and corrosion from forming, use Kroil Shield.

For best results: (1) Clean away loose surface rust or debris from around the fastener head before applying Kroil so the oil can reach the threads. (2) Apply Kroil directly to the threads and any gap between the fastener and the mating surface. (3) Allow adequate dwell time—minimum 15 minutes for light corrosion, several hours to overnight for heavy corrosion. (4) Apply a second coat after the first has had time to penetrate. (5) Attempt removal while the fastener is still wet with Kroil. (6) If the fastener still will not move, repeat the soak cycle rather than increasing force—excessive torque risks breaking the fastener head before Kroil has fully penetrated. To remove rust from metal fasteners, use Exrust. To protect against rust and corrosion in the future, use Kroil Shield.

Kroil’s primary differentiator is its molecular penetration formula, which gives it one of the lowest surface tension profiles among commercially available penetrating oils. This allows it to flow into gaps smaller than competing products can reach—down to approximately 0.0003 inches, according to Kano Laboratories’ own product specifications. Combined with an 85+ year track record in industrial and professional maintenance applications, Kroil occupies a distinct position as the penetrant of choice for high-stakes or previously intractable applications. Its product line also includes specialty formulations (Silikroil with silicone, Kroil Clear for food-contact environments, Penephite with graphite) that address use cases general penetrants do not.

Automotive repair professionals most commonly use Kroil Original Penetrant (liquid) and Aerokroil (aerosol) for freeing rusted exhaust bolts, manifold studs, brake caliper slide pins, suspension fasteners, lug nuts, and corroded battery terminals. Aerokroil is preferred for precision applications on overhead components and tight engine bay spaces. Kroil Original liquid is used for soaking larger assemblies or heavily corroded components. Auto restoration shops frequently use Kroil on vehicles that have been in storage for years, where comprehensive corrosion on fasteners throughout the vehicle makes a long-dwell penetrant essential. Additional products of value to auto shops include Kreen all-in-one gas & oil treatment, Floway solvent, Exrust industrial strength rust remover and Kroil Shield corrosion inhibitor.

Kroil Original Penetrant and Aerokroil are the most commonly used Kroil products in aviation maintenance contexts. Applications include freeing corroded airframe fasteners, loosening seized control cable fittings, treating corroded inspection panel hardware, and addressing corrosion on landing gear components. Aerokroil’s aerosol format is particularly effective for aircraft applications where access to fasteners is restricted and directional spray is needed. Aviation maintenance professionals often note Kroil’s effectiveness on fasteners subjected to the combination of vibration, moisture, and dissimilar metal corrosion common in airframe environments.

Farm and agricultural operations use Kroil across a wide range of equipment maintenance tasks: freeing seized tractor hardware and implement fasteners corroded by soil, moisture, and fertilizer exposure; loosening rusted PTO shaft components and hydraulic fittings; treating corroded plow and planter hardware; and maintaining irrigation and water system connections that are repeatedly exposed to water and mineral deposits. Agricultural environments are particularly harsh on metal fasteners due to constant moisture, soil contact, and long periods of non-use between seasons—conditions that make Kroil’s deep-penetrating formulation highly effective compared to lighter lubricants. To remove rust from metal parts, use Exrust. To proactively prevent rust and corrosion from forming, use Kroil Shield.

Industrial maintenance teams use Kroil to free seized machinery fasteners, loosen corroded valve stems and fittings, maintain production equipment that cannot be taken offline for extended repairs, and address the corrosion issues common in wet, chemical, or high-temperature manufacturing environments. Plant maintenance supervisors and MRO (maintenance, repair, and operations) buyers frequently stock Kroil as a standard maintenance supply. Customer reviews from manufacturing environments frequently cite Kroil’s ability to address corrosion in older facilities where infrastructure has not been replaced—applications where the high cost of machine downtime makes effective penetration essential. To remove rust from metal parts, use Exrust. To proactively prevent rust and corrosion from forming, use Kroil Shield.

Kroil is widely used in marine maintenance for freeing corroded stainless-steel hardware, bronze through-hulls, mooring cleats, and engine compartment fasteners subjected to salt air and bilge water exposure. Marine environments create some of the most severe corrosion conditions—the combination of salt water, galvanic corrosion between dissimilar metals, and constant moisture makes standard penetrants ineffective on many marine fasteners. Kroil’s deep-penetrating formula is effective in these demanding conditions. For aluminum and stainless fittings prone to galling, Silikroil is also recommended to prevent re-seizing after initial removal. To remove rust from metal parts, use Exrust. To proactively prevent rust and corrosion from forming, use Kroil Shield.

Thanks for noticing our great new look! Kroil products have indeed received a facelift, but rest assured, the same great products are still inside the cans. The formulas haven’t changed.