Why 20 PPI Filter Foam Works Well for Aluminum Casting

Author : Leslie Du | Published On : 28 Apr 2026

In aluminum casting, melt cleanliness has a direct impact on final part quality. Even when the alloy composition is correct, non-metallic inclusions such as oxide films, slag, and dross can still create problems during solidification. These contaminants often lead to surface defects, porosity, poor machining performance, and lower mechanical strength. That is why ceramic foam filters are widely used in foundries. They help remove unwanted particles from molten aluminum before the metal enters the mold cavity. Among the available grades, 20 PPI is often considered one of the most practical choices for general aluminum casting. The reason is simple: it offers a good balance between filtration efficiency and metal flow. A filter that is too coarse may let more inclusions pass through, while one that is too fine can slow the filling process or increase the risk of misruns in some applications. For many foundries, a 20 PPI filter foam provides reliable filtration without creating excessive flow resistance. Another benefit is flow stabilization. As molten aluminum passes through the ceramic structure, the metal stream becomes more uniform and less turbulent. This helps reduce the formation of new oxide films during pouring, which is just as important as removing the inclusions already present in the melt. Of course, filtration works best when combined with proper melt treatment, good gating design, and correct pouring practice. But as a final control step, the right foam filter can significantly improve consistency from batch to batch. For foundries producing aluminum castings on a regular basis, choosing the right filter grade is a small decision that can make a noticeable difference in scrap rate and overall casting quality.