QIB Standard

Introducing the Machu Test – Industrial Physics

The Machu test is a rapid, accelerated corrosion test used to check the quality of organic coatings on aluminum and steel. A coated panel is scribed through to the base metal, immersed in an aggressive acidified salt and peroxide solution at a controlled temperature, and then assessed for how far corrosion has crept beneath the coating from the scribe. In a matter of hours it gives quality and R&D experts an early read on coating and pretreatment quality that would otherwise take a far longer salt spray program to reveal.

The method is not a standalone ISO or EN standard. Instead it is prescribed within two well-known coatings quality specifications: the QUALICOAT Specifications for architectural coatings on aluminum, and the quality regulations of QIB (Qualitatsgemeinschaft Industriebeschichtung e.V.), the German Quality Association for Industrial Coatings. Both use the Machu test as a fast, in-house check of coating integrity.

What the Machu Test Covers

The Machu test sets out an accelerated way to evaluate the corrosion resistance of a coated metal surface, focusing on how well the coating and its pretreatment resist undercreep at a defect. Key elements of the method include:

• An immersion (dip) test in an acidified solution of sodium chloride, glacial acetic acid, and hydrogen peroxide, held at a controlled elevated temperature
• A defined scribe cut through the coating down to the base metal, made with a purpose-built scratching tool (the scribe follows the guidance of ISO 17872)
• Assessment of corrosion infiltration, or undercreep, measured outward from the scribe line after the immersion period
• Application to coated aluminum and steel, including powder-coated and liquid-coated architectural profiles

Within QUALICOAT the method appears as an accelerated corrosion test on extruded aluminum sections. Within the QIB quality regulations it is a mandatory self-inspection test for the quality of pretreatment.

Why the Machu Test Matters

Coating failure on architectural aluminum or coated steel is expensive, visible, and slow to appear in service. The Machu test matters because it surfaces problems early, before coated product leaves the plant. A standardized rapid corrosion check helps quality, R&D, and operations experts to:

• Screen pretreatment and coating quality in hours rather than the days or weeks a full salt spray program requires
• Catch weak adhesion and poor pretreatment that would later show as undercreep, blistering, or delamination in the field
• Support QUALICOAT and QIB quality-label requirements, where the Machu test is a specified in-house or inspection test
• Provide an objective, repeatable basis for supplier qualification and for resolving disputes between coater and customer
• Reduce waste, rework, and warranty risk by verifying batches before they ship

How the Machu Test Works

A coated test panel is first scribed crosswise through the coating to the bare metal using a controlled scratching tool, so there is a defined defect for corrosion to attack. The panel is then fully immersed in the heated test solution, which combines sodium chloride, glacial acetic acid, and hydrogen peroxide to create a deliberately aggressive, low-pH environment. Because the reaction is driven by that chemistry and by temperature, the bath is held at a stable elevated temperature for the duration of the test.

After the immersion period the panel is removed and examined. The key result is the infiltration, or undercreep – how far corrosion has spread sideways beneath the coating from the scribe. A tight, well-controlled result indicates sound pretreatment and coating adhesion; wide undercreep points to a weakness in the system. Keeping the temperature and solution chemistry consistent is what makes the result repeatable and comparable from one test to the next, which is exactly what a controlled test bath is designed to deliver.

Machu Test Equipment

The TQC Sheen Machu Test Bath, part of the Industrial Physics group, provides the controlled conditions needed to run the Machu test to QUALICOAT and QIB specifications.

This temperature-controlled bath is built to hold the test solution at a stable, closely regulated temperature throughout the immersion period, so results stay accurate, repeatable, and reliable. Typical features include:

• Precise temperature control and monitoring for consistent test conditions
• A capacity sized for standard Machu test panels and containers
• A timer to manage the immersion period without constant supervision
• A design intended for routine quality control use in coating and finishing operations

The Machu Test Bath supports coating performance testing to QUALICOAT and QIB specifications, and pairs with a compatible scratching tool to prepare the scribe. If you are unsure how the bath fits your current pretreatment or coating line, our experts can help you work it through.

Related Standards and Specifications

The Machu test sits within a wider family of coating quality specifications and corrosion test methods. Those commonly referenced alongside it include:

• QUALICOAT – international quality label for liquid and powder organic coatings on architectural aluminum, which specifies the Machu test
• QIB (Qualitatsgemeinschaft Industriebeschichtung e.V.) – German quality association whose regulations require the Machu test for higher coating stress groups
• GSB International – the other main European quality mark for coated aluminum, which also uses the Machu test
• QUALISTEELCOAT – quality label for organic coatings on steel
• EN 12206-1 and EN 15773 – European standards for powder coating of aluminum, and for powder coating of galvanized steel
• ISO 9227 – salt spray tests (including acetic acid salt spray), the standardized corrosion test the Machu method is often compared against
• ISO 17872 – guidance on scribing coated panels for corrosion testing, which governs the Machu scribe

Your Global Test and Measurement Partner for Coating Quality

Industrial Physics supports quality, R&D, and operations experts around the world with the paints and coatings test and measurement expertise needed to work confidently with methods like the Machu test. Whether you are qualifying a new pretreatment, meeting a QUALICOAT or QIB requirement, or investigating a coating failure, we can help you achieve accurate, repeatable, and reliable results.

Get in touch to talk through your coating corrosion testing requirements.