IronClad Standard Duty Bolt Cap

NTC Wind Energy's patented Ironclad™ Standard Duty bolt caps were the original caps in the wind industry and remain the standard of the industry. NTC Wind Energy's Ironclad™ Bolt Caps are specifically designed to seal against the tower flange and create a protective environment for the grease applied to the rod, nut and washer. In addition to preventing the dissipation or breakdown of the grease applied to the metal, bolt caps prevent water from traveling down the threads and into the bolt sleeve within the foundation.

Our Standard Duty bolt caps are made from high-density polyethylene and are UV resistant to assure the long-term protection of your investment. We are so confident in our caps that we guarantee them for five years with our installation service (excluding damage caused by external factors such as fire, sheet ice, animals or humans).

IronClad Standard Duty Bolt Cap Specifications Bolt Cap Installation Instructions

IronClad Super Duty Foundation Anchor Bolt Cap

We are proud to introduce an all new foundation anchor bolt cap designed to combine all of the best features of the IronClad Standard Duty bolt cap and the IronClad Extreme Duty bolt cap and more.


  • Integrated O-ring – No need to install the o-ring during cap installation.
  • Vented – Integrated water proof vent to prevent vacuum water draw.
  • Polypropylene Copolymer Construction – Built for the same strength and durability as our Extreme Duty bolt cap.
  • Universal Fit – Fits rod projections from 10 to 16 inches and rod sizes from #10 grade 75 to #11 – 150 KSI.
  • Quick Shipment – Our caps are made right here in the USA from domestically sourced materials. Due to the universal fit and advanced manufacturing, we are able to stock large quantities and ship on your schedule.
  • Easy Installation – Can be installed with no tools, removed and reinstalled without damage to the cap or foundation components.

NTC Wind Energy has been your bolt cap supplier for over 20 years and we have listened to the needs of our customers throughout the wind industry. The IronClad Super Duty foundation anchor bolt cap answers those needs and we are confident that you will agree. Please give us a call today at 1-800-359-0372 or just select “Get a Quote” on this site and we will be honored to help you with your product needs.

IronClad Extreme Duty Bolt Cap

NTC Wind Bolt caps

This patent pending bolt cap was designed and built to address the need for a heavier-duty cap, providing even more protection against moisture intrusion and more resistance against damage due to the elements.

The Extreme Duty Bolt Cap incorporates four sealing surfaces, including an o-ring, two retaining rings which bottom out on the tower flange under compression, and a flexible skirt on the outside of the cap which also compresses against the tower flange. These four redundant seals provide maximum protection against the intrusion of moisture. This is especially important for coastal installations, where corrosive salt water is present.

At the top of the cap, we have incorporated a grease injection port for even more protection. Warmed wax-based grease can be injected or poured thru the port. The liquid grease congeals around the bottom seal as it cools, providing an extra measure of protection against corrosion of the washer and the base of the nut. The injection port is protected by a hexagon-shaped top cap, which reseals the entry point. 

There are four heavy gripping fins inside the cap, which provide a very tight and secure installation, while also providing for fast removal for re-tensioning.

The Extreme Duty Bolt Cap was built to resist impact damage from sheet ice. We’ve added extra material to the top of the cap and brought the interior fins all the way to the top, adding additional structural strength to the cap. This cap weighs a full 13 ounces and is made of thick polypropylene with the maximum amount of added UV stabilizer, making it by far the toughest and longest lasting cap in the industry.

For serious protection against corrosion of your foundation anchor bolts in harsh environmental conditions, nothing beats the IronClad Extreme Duty Bolt Cap. We welcome your inquiry for pricing and availability.

IronClad Extreme Duty Bolt Cap Specifications