For the aerospace industry, hard chrome plating has been the go-to solution for manufacturers for more than six decades. But with the health and environmental concerns of this commonly-used deposit well known – and with legislation in US bringing the reign of hard chrome plating to an end – now is the time to seek a viable alternative.
To manufacturers operating within the aerospace industry, the benefits of hard chrome plating are clear to see. It has been – and, particularly for military applications, continues to be – a critical process both in terms of manufacturing and maintenance, providing surfaces which are wear and corrosion-resistant for essential equipment, from hydraulic piston rods and propeller hubs to landing gear, gear shafts and gun barrels.
A Wide Range of New Technologies
Manufacturers are able to choose from a wide range of technologies, none of which use hexavalent chrome. These include various spraying techniques such as thermal spray, PVD and CVD, however, these methods require a high temperature, high vacuum, or high melting point for the substrate. There is also a new breed of super steels. Yet while each has advantages, they also have drawbacks including – in the case of new alloys – the fact they are costly and still unproven over time.
As a result, deciding which to choose can be challenging. Added to this, the aerospace industry is typically cautious. Any change – particularly one of this scale – is perceived to have a high level of risk involved. With particular attention to the components manufactured for the aerospace industry, many are designed to function for several decades without the need for maintenance, so their service longevity must be guaranteed.
Challenging the Dominance of Hard Chromium Plating
In finding an alternative, the problem lies in the dominant suitability of hard chromium plating for the aerospace sector. It performs at extremely high temperatures, has excellent corrosion and wear resistance and, together with hardness levels of 700-1,000HV, delivers an excellent surface finish across a wide range of applications. With all of these attributes, finding an alternative solution which covers all bases is challenging.
A New Way of Thinking
There are many alternatives to chromium plating, but none are quite so universal in their application. As a result, the industry is being forced to think a little differently. Rather than striving to find a direct and complete replacement for all applications, it is perhaps better to find solutions which deliver results for specific applications. For example, a part might require the wear properties of chrome plating, but not its hardness or corrosion resistance. Equally, hard chrome plating typically has a higher co-efficient of friction than nickel-tungsten, making it less suitable for certain components. So, instead of it being a case of ‘one for all’, it is time to think about ‘many for specific’.