High-quality castings and forged parts are commonly and successfully galvanized. The quality of the galvanizing is strongly influenced by the quality of the casting. As with all steel to be galvanized, cleanliness is very important to achieve completely galvanized cast iron or steel parts. However, conventional cleaning processes employed by galvanizers do not always adequately clean castings. This is because sand and other surface inclusions are not removed by chemical cleaning. Thorough abrasive cleaning is the most effective method for removing foundry sand and impurities. In fact, the preferred way to clean the casting is by abrasive blasting (either grit-blasting or a combination of grit and shot). Cleaning is traditionally performed at the foundry before shipment to the galvanizer. However, some galvanizers are able to perform abrasive blasting at their facilities - check with your galvanizer before sending your parts.
Sound, stress-free castings with good surface finishes will produce high-quality galvanized coatings. The following design and preparation rules should be applied for castings to be galvanized:
· Avoid sharp corners and deep recesses
· Use large pattern numerals and generous radii to facilitate abrasive cleaning
· Specify uniform wall sections. Non-uniform wall thickness in certain casting designs may lead to distortion and/or cracking. Cracking results from stress developed as the temperature of the casting is increased during galvanizing. Uniform wall sections and a balanced design lowers stress.
As always, if you have any questions regarding this or any other galvanizing topic, please don't hesitate to contact us: