Corrosion Improvements for Hardchrome
Hard chromium deposits are widely used for the provision of hard, abrasion resistant wearing surfaces and for the building up of undersized and worn parts. The value of chromium for such purposes lies in its hardness, resistance to abrasion, passivity of surface, and its "anti-seize" properties when applied to rotating or reciprocating parts.
Newcastle based Jarvie Engineering Pty Ltd specializes in the manufacture and repair of hydraulic cylinders for use in the underground and open cut coal mining industry. Hydraulic cylinders used in underground longwall roof supports use water rather than oil as the hydraulic medium, placing strong demands on the coatings of the sealing surfaces. Add to this the acidic ground water combined with airborne coal dust and sometimes hydrogen and sulphur based gasses, and it is no wonder that typical hardchrome or copper based coatings can often fail.
General Manager Trevor Anderson explains that hardchrome has inherent micro and macro cracks that allow the penetration of corrodents through to the underlying steel base metal. As the metal corrodes it expands, breaking the bond between the chrome and steel. This initiates "blister" damage to the sealing surfaces as well as damage to the seals, leading to system failure.
For the last 15 years, and where this type of failure has occurred, Jarvie have been treating chrome with a product named Cr3 that greatly improves the corrosion resistance of the surfaces by preventing the ingress of any corrodent. The Cr3 takes advantage of the weakness of chrome, by filling and sealing the inherent cracks and pores. It is best applied immediately after the chroming process before hydraulic cylinder assembly or use. The coating provides several other advantages including improved lubricity; improved release properties, galling is virtually eliminated and wear resistance is greatly extended.
Jarvie Engineering has their own in-house chrome plant to assist and provide prompt turnaround of cylinders under repair. This process is backed up by two laser cladding systems, installed in 1998 to provide many other corrosion and wear resistant coating opportunities for wide variety of critical machine parts.
More Information
Trevor Anderson
www.jarvie.com.au
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