Is Industrial Hard Chrome Plating Still Your Best Enhancement Solution?
In the 2000 film Erin Brockovich, Julia Roberts plays the title character legal clerk turned environmental activist. The events depicted in the movie are based upon the environmental concerns in Hinkley, California. The investigation looked into the contamination of groundwater supplies with chromium-6, more commonly known as hexavalent chrome. A local power company had been using chromium-6 in some of their compressors to reduce corrosion. This chromium-6 contaminated water would then be discharged into unlined pools. This water then leaked into the local groundwater supply. Hexavalent chrome is recognized by the EPA as a hazardous air pollutant, a priority pollutant under the clean water act and a hazardous constituent under the resource conservation and recovery act. This same compound is the one used in industrial hard chrome plating.
So Why Use It?
Chrome plating has been around, in various forms, since the early 1900’s and has been used to increase the wear resistance of industrial components for almost just as long. Its long history lends to it being a well-researched and well implemented process. It can easily coat inner diameters and intricate geometries with a high wear-resistant material. Hard chrome plating can achieve a hardness of 700 to 1,000 Vickers. Not only is chrome plating hard, it is also thin. Hard chrome plating is typically deposited from 0.001 inches to 0.004 inches thick, making it good for components in tight tolerance environments. Hard chrome plating also reduces friction, achieving a surface finish of approximately 1 Ra. At a glance, hard chrome plating seems to be the perfect industrial coating solution for hydraulic rods, crane and lift cylinders and hydraulic pump components; but it has limitations.
The process of hard chrome plating is rather complicated and lengthy. Components must be completely submerged plating liquids and transferred to various large tanks depending upon the size of the part. This creates size limitations and high turnaround times. These large tanks are easily contaminated, and those plating imperfections could severely impact performance in the field. Since the whole part must be submerged, it also means that masking areas that should not receive plating is very difficult. This is process is also limited in the materials it can apply and the thicknesses it can achieve.
The process of hard chrome plating is performed by electroplating. Electroplating uses electrical conductivity to apply plating to the surface of a component. This limits the material that hard chrome plating can be applied to. A component must be made of steel, stainless steel, brass, bronze or copper. This will fit most machine components but will fall short on specialized or ferrous materials.
The elephant in the room is the environmental concerns surrounding the disposal of the materials used in chrome plating. During the chrome plating process, chromium is dissolved into the electrolyte solution and becomes very hard to safely dispose of afterwards. If chromium reaches the local groundwater supply, it can cause illness and some even believe it to be a carcinogen. Hard chrome plating has many advantages; but at what cost?
Is There Something Better than Hard Chrome?
If the cost is too great, is there an alternative? In recent years, thermal spray technology has advanced leaps and bounds and readily competes with hard chrome plating. Thermal spray uses combustion to heat up metallic materials and apply specialized coatings to industrial surfaces. It is like spray painting with metal. Thermal spray has the same wear resistance as hard chrome plating while achieving more corrosion resistance.
A Multitude of Materials
Due to its nature of application, thermal spray can be customized using various materials to produce precise coating characteristics. Thermal spray can be applied to the same component materials as hard chrome plating but also some that chrome cannot. Common hard chrome alternatives include tungsten carbide and chrome carbide. While chrome carbide also contains chromium, it is in solid form and in smaller amounts. It is easily contained and disposed of in an environmentally conscious manner. Specialty materials such as Chrome Carbide Hastelloy and Tungsten Carbide Chrome Carbide Nickel can also be used depending upon the corrosion, wear and operating temperatures you may be trying to mitigate.
More Coating Thicknesses
Thermal spray can be applied down to thicknesses of 0.0015 inch and up to thicknesses of 0.060 of an inch. This can be advantageous when compared to the thicknesses you can achieve with hard chrome. Thermal spray coatings can be built up during spray to exceed the desired dimensions and then machined down to meet tight tolerances. You can also layer coatings for larger build up or for different properties of the coating system. The machinability of thermal spray coatings also lends itself to a variety of polishing capabilities.
Comparable Surface Finish
Thermal spray coatings can be applied at various surface finishes. High velocity air fuel spray, for instance, has an as sprayed roughness of 40 Ra at a thickness of 0.002 inches. This same coating can be finished down to less than 1 Ra by grinding and polishing. These coating characteristics are the same as those of hard chrome plating but with the added corrosion and impact resistance benefits of thermal spray.
Winning Alternative to Hard Chrome
Thermal spray can achieve similar coating characteristics in respect to hard chrome plating but with a smaller environmental footprint. In addition to being environmentally conscious, thermal spray is also inherently corrosion resistant whereas hard chrome plating is only corrosion resistant with additional steps and treatments. The ease of the thermal spray process lends to faster turnaround times and less contamination issues compared to hard chrome plating. Thermal spray can also be portable; meaning it can be brought on location for parts that are too large to transport.
If we take a look back at the Hinkley water contamination, could thermal spray have been the solution to keep corrosion from damaging the cooling water sections of their compressors? While thermal spray will never fully replace hard chrome plating in some instances; it is a valuable alternative for hydraulic rod enhancement, pump component enhancement, and much, much more. For more information, read about our hydraulic cylinder repair or contact us today to see if thermal spray is the solution for you.
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