“Cast materials are notorious for presenting [surface] finishing challenges. It’s not just what’s on the surface, it’s also what lays beneath!”
Getting good surface finish on alloy castings
A recent metal finishing job presented a challenge to A Class Metal Finishers of Lonsdale, SA. The customer required a highly polished and bright chrome (mirror-like) finish on goods to be supplied to a discerning and fussy customer base.
Cast materials are notorious for presenting finishing challenges. It is not just what is on the surface, it is also what lays beneath. Pitting and porosity can be present within the metal structure of the casting.
Casting inclusions (small lumps or impurities) can be uncovered or ripped away in the polishing process and expose small holes and craters randomly across the surface.
Zinc die-cast porosity in particular is like a disease in the metal (commonly seen in old chromed car parts requiring restoration) and can worsen over time if exposed to oxygen and the environment.
A nice bright chrome finish with a bunch of random pit holes across the surface is not what most customers want. (But in many cases – that is just what they settle for)
With many years experience in restoration of many types of metals as well as preparing and finishing a variety of production items, A Class Metal Finishers has learned many tricks for preparing, repairing and sealing underlying impurities in castings.
Says Director, Greg Wood “although they can present a finishing challenge, cast products have many benefits to offer the manufacturer and the customer (mainly it’s cheaper) and with our ability to achieve good quality surface outcomes, through our range of techniques, innovative equipment and experience, together with the manufacturer we can usually find a good quality and importantly, good value outcome”.
“New technology such as dynamic vapour deposition plays an important role in our ability to revolutionise the way castings are treated. It basically enables us to rebuild small surface areas, eliminating many casting imperfections and enabling production of some very high quality surface finishes” Greg Wood says.