Large scale boronizing was first applied to drive gears for petrol-driving engines in 1979. Meanwhile, similar helical gear pairs have long-since become standard fittings in vehicle and stationary engines.

Boronizing or “BorCote™” is a thermochemical surface hardening process in which boron atoms diffuse into a metal surface to form hard boride layers. These very hard borides have been proven to be excellent for protection against wear.  BorCote™ is our proprietary process that utilizes a proven patented chemical that transforms the surface structure of the steel into one that resists ABRASION, CORROSION,  and EROSION.  Our process can be applied onto complex parts with unorthodox geometries and will maintain uniform layer thickness.  This new surface will not flake or peel, and is impact resistant.  

The process is carried out by preparing the part accordingly, packing it in a container suitable to size of the part, then filling the container with the boron powder. The parts are then exposed to temperatures ranging from 800 to 1050˚C and takes from one to several hours. The temperature and time required depend on the material to be boronized and on the desired thickness of the boride layer.

Existing conditions or requirements may necessitate heat treatment either before or after boronizing or both.

Heat treatment either before boronizing takes the form of:

  • Stress-relief annealing
  • Blank Hardening

And after Boronizing, of:

  • Diffusion annealing
  • Hardening/tempering

Most steels of the construction, case-hardened, tempered, tool-making and chemically-resistant types lend themselves to boronizing.  Various steels such as:

  • Carbon steel
  • Alloy steel
  • Stainless steel
  • No-Resist Cast steel
  • Tool steel

Other suitable materials are Aromco iron, cast iron, sintered iron and steels.

Hard metals are readily boronized, particularly the sintered types based on WC-TiC with C or Ni as a binder. 


Boronized steels are extremely resistant to abrasion on account of their great hardness, commonly exceeding 80+ or higher Rockwell ‘C’ hardness and will not flake or peel and is impact resistant. Boride layer thicknesses vary with application and increase service life by several-fold. Some examples requiring protection from abrasive wear include pneumatic transport systems, plasticating units in plastics processing and parts for mills, pumps and valves. 

The clear superiority of boride layers, particularly at high temperatures, over other coatings such as Gas Nitride and Salt-bath nitro-carburide are well documented.

The good wear properties of boride layers and the use of less lubricant or none at all, will become ever more important in the future, since developments are heading in the direction of severe curtailment of lubricant use in order to protect the environment.

  • Abrasion, Corrosion, Erosion Protection    
  • High Hardness (75HRc ++)    
  • Uniform Diffusion (Layer Thickness)    
  • Beyond Line Of Sight Coverage    
  • Impact Resistant    
  • Passed ASTM G65 (6000 Revs.)    
  • Passed NACE TM0185 (autoclave 1000psi, 100°C, H2S + CO2 + Salt Brine)


This process can be applied on complex parts with unorthodox geometries or areas beyond line of sight and will maintain uniform growth. Consider this coating for:

  • High Flow Areas    
  • Sand Control    
  • Pumps (ESP, Centrifugal)    
  • Frac Components (Landing Nipples, Slick Joints, Seat Nipples)
  • SAGD Components (Valves, Fittings)

Some examples of other applications include the service life of boronizing grinding disks for commercial coffee roasting plants is five times as great as that of non-boronized disks. Chain links for conveyor equipment in silo towers are forged parts. Complete transport chains are currently being tested in boronized form. The results for abrasion and for corrosion are much better than those for non-boronized chains. Casting tubes in continuous casting equipment for zinc, last more than 15 times longer when boronized. Good results have been achieved by a construction that facilitates boronizing. Boronizing effectively protects balls for ball valves against abrasive wear. These types of boronized valves are used in equipment for transporting gases or liquids with a high solid-abrasive content, such as in off-gas scrubbing and in the petroleum industry. 

Silver Fox BorCote™ Capabilities

Silver Fox has the capability of boronizing parts up to 6’ in length with various diameters and offers two versions of this process.


  • Our standard powder blend. This version should be considered for moderate to high abrasion and erosion.


  • Our premium powder blend that offers extreme abrasion and erosion protection where required. 


On account of their outstanding abrasion resistance, boride layers are used to reduce abrasive and adhesive wear. Boronizing is most frequently adopted for steels and nickel alloys. Attainable layer thicknesses vary according to material and application. There are a large number of possible applications for boronizing in mechanical, equipment and apparatus engineering.