Why this test matters
Powder-coated aluminium used in architectural applications, window frames, facades, curtain walls, must resist corrosion for decades outdoors. The MACHU test, prescribed in the Qualicoat specifications, evaluates exactly that: how well a coating on aluminium protects the metal beneath it, and how far corrosion spreads once the coating is damaged. It's the standard qualification test for coated aluminium extrusions used in construction and architectural applications, revealing weaknesses that a slower, real-world exposure test would take years to show.
How the test works
Before testing, a 1 mm-wide cross-cut incision is made through the coating down to the bare metal. The sample is then immersed in a solution of sodium chloride, acetic acid, and hydrogen peroxide at 37°C for 48 hours, a combination that accelerates corrosion far faster than natural exposure or a standard salt spray test. Afterward, the sample is rinsed and inspected for corrosion, blistering, and detachment, with particular attention to how far corrosion has infiltrated from the scribed line.
What you learn from this test
You get a clear, visual assessment of how well your coating protects its substrate: whether it blisters, detaches, or lets corrosion spread from a damaged area, and how far. Because the test is fast, just 48 hours, it works well as a screening tool to compare coating systems, validate a surface treatment, or qualify a supplier before committing to slower, longer-term corrosion testing. The results support confident decisions on coating selection and Qualicoat compliance.
