When abrasive blasting delicate aluminum trim components, what specific media material and precise pressure range must be selected to effectively remove oxidation without causing peening, surface distortion, or significant material removal?

When abrasive blasting delicate aluminum trim components to effectively remove oxidation without causing peening, surface distortion, or significant material removal, the specific media material that must be selected is sodium bicarbonate. Sodium bicarbonate, commonly known as baking soda, is a highly friable and non-abrasive media that shatters upon impact, making it ideal for removing contaminants like oxidation without etching or damaging the substrate. Oxidation refers to the dull, often whitish or grayish, layer of aluminum oxide that forms on the surface of aluminum due to chemical reaction with oxygen. The precise pressure range for blasting with sodium bicarbonate on such delicate surfaces must be maintained between 10 to 25 pounds per square inch (PSI). This low pressure is crucial to ensure the media's impact energy is sufficient only to dislodge the brittle oxidation layer. "Peening" is the process of cold working the metal surface through impacts, inducing compressive stresses that can cause hardening and, on thin materials, undesirable deformation or "surface distortion." By using sodium bicarbonate at this low pressure, the process effectively removes oxidation while preventing peening, preserving the dimensional integrity, and avoiding any significant material removal from the delicate aluminum trim.