The followings are some common surface finishing and treatments to sand casings. Some works could be completed in metal foundries, some may need to be entrusted to professional workshops.
Linishing and Fettling
Fettling removes risers and excess material from the sand casting, whilst linishing involves grinding or sanding the component, which improves the surface flatness.
Shot Blasting and Peening
These processes give the casting a uniform appearance and remove sand or small burrs and provides a good key prior to next-stage processes such as painting or powder coating.
There are a wide range of painted finishes, including powder coating, suitable for castings that require high levels of resistance to abrasion and contact. Wet painting is another common process and provides a high level of coloured finish.
Hard coating anodising produces increased corrosion resistance and protects the surface. Chromic acid anodising produces a thinner film which remains tough and also provides a good key for painting, while sulphuric acid anodising produces a thicker film.
Alochroming, also known as chromating or alodining, is a chemical treatment used to improve the durability and surface finish of aluminium and other metals. This will produce a decorative finish but is not ideal for components that will be exposed to significant abrasion.
This will increase the resistance of sand castings to withstand extreme temperatures, making it ideal for components that experience adverse weather and temperatures, such as those in aerospace and aviation.