Aluminum alloy surfaces turning black or developing spots after cleaning is a common problem faced by many precision machining companies. The root cause, in over 90% of cases, lies in the pH value selection of the cleaning agent.
Aluminum's 'Sensitive Nature'
Aluminum is an amphoteric metal, soluble in both strong acids and strong bases. When the pH of a water-based cleaner exceeds 9.0, even with corrosion inhibitors present, mild chemical corrosion may occur on the aluminum surface, manifesting as blackening, darkening, or spotting.
pH Value Selection Guide
For aluminum alloy workpieces, we strongly recommend choosing neutral or weakly alkaline cleaners with a pH between 7.0-8.5. Our TS-W100 Aluminum Alloy Water-Based Cleaner has a precisely controlled pH between 7.0-8.0, combined with high-efficiency corrosion inhibition technology, ensuring aluminum parts remain bright and clean after cleaning.
Other Precautions
1. Cleaning temperature should not exceed 70℃. 2. Rinse immediately with pure water and dry after cleaning. 3. Different aluminum alloy grades have different pH tolerances — sample testing is recommended first.