Corrosion Resistance and its Improvement on EDM'd Surface in Molding Process of Plastics

Abstract

In the injection molding process of plastics, some out gas generated from their plastics may attack the structure of the molding dies and cause corrosion. Especially EDM'd dies could be damaged on the corrosion process.
This paper deals with the corrosion resistance and its improvement on EDM'd surface in the molding process of plastics. An autoclave test method with plastics powder was used to evaluate the corrosion resistance.
The results are summarized as follows; 1) In general, corrosion grows up as a pit from the micro-cracks generated on EDM'd surface. 2) However, a smooth and/or a crack-free surface EDM'd under the workpiece positive polarity with micro-power discharge give relatively high corrosion resistance. 3) Heat treatment conditions for the specimen before EDMing influence on the corrosion process. 4) Subsequently, a glass beads blasting method for EDM'd surface could be hopeful to improve the corrosion resistance.