Worn and corroded molds frequently cause downtime for both captive and job shop plastics molders and metal formers.
In PVC molding, corrosion is commonly caused by hydrocholric acid. Hydrochloric acid is a byproduct generated by incipient decomposition during the molding of polyvinyl chloride, as well as of other polymers. The liberated acid etches or pits the mold cavity. By selectively depositing a thin layer of gold in areas where the acid tends to pocket, the pitting can be eliminated.
Another common cause of corrosion happens when a mold is out of production and in storage. To prevent the base steel material from corroding while out of service, mild steel molds are frequently selectively plated with cadmium while out of production for extended periods of time. Cadmium, because of its position relative to iron in the electromotive force series, will actually form a galvanic cell with the steel and preferentially corrode sacrificially, thus protecting the steel.
In the next blogs, you’ll learn about other applications that selective plating is suitable for, including:
- Resizing Core Pins and Bushings
- Flash Correction
- Machine Maintenance