ASTM G46: Pitting Corrosion Examination Testing Services

Scope

ASTM G46 evaluates pitting corrosion by providing procedures to measure pit depth, density, and distribution on metal surfaces. The test enables quantitative and qualitative assessment of localized corrosion damage.

ASTM G46 evaluates:

• ASTM G46 is a standard guide, not a standard test method, and it’s intentionally written to describe a selection of procedures rather than a single rigid protocol.
• Both destructive and non-destructive approaches to examining pitted metal surfaces are covered, letting the lab choose the technique that fits the component and the question being asked.
• Coverage extends broadly to metals and alloys that are susceptible to pitting, including stainless steels, aluminium alloys, and other corrosion-resistant materials.
• Pit density, distribution, size, and depth are all addressed through consistent visual and measurement-based approaches.
• Standardized reference charts, introduced by the guide, help technicians classify pit density and pit size in a repeatable way across different operators and labs.
• Several recognized pit morphologies are described as well, including narrow-deep, elliptical, wide-shallow, subsurface, horizontal, and vertical pit shapes.
• G46 outlines the concept of the pitting factor, a ratio used to compare the deepest observed pit penetration against the average metal penetration across the surface.
• It’s written to support both field inspection of in-service components and controlled laboratory corrosion testing programs.
• Oversight comes from ASTM Subcommittee G01.05 on Laboratory Corrosion Tests, part of Committee G01 on Corrosion of Metals, which maintains the guide.
• It also works alongside related corrosion-testing standards, serving as the common reference point for describing pitting once other tests have induced or revealed it.

Applications

• Root-cause and forensic failure analysis of piping, tanks, and pressure equipment that failed prematurely in service.
• Remaining-life and fitness-for-service assessments on aging infrastructure exposed to chloride-bearing or otherwise corrosive environments.
• Material selection and qualification testing when comparing candidate alloys for a new design or upgrade.
• Evaluating corrosion inhibitor or coating performance in laboratory exposure programs.
• Quality assurance and incoming-material inspection for components destined for marine, offshore, or chemical-processing service.
• Post-exposure characterization following accelerated corrosion tests such as salt spray or cyclic immersion testing.
• Research and development work studying alloy behaviour in oilfield, desalination, or other aggressive service chemistries.

Benefits

• A consistent, industry-recognized vocabulary makes it possible to describe pit density, size, depth, and shape the same way across different labs and reports.
• Run/repair/replace decisions become objective and data-backed, rather than subjective visual judgment calls.
• Engineering teams can compare alloy or coating performance on an apples-to-apples basis.
• Failure-analysis reports and insurance or warranty claims gain strength from standardized, defensible documentation.
• The risk of unplanned outages drops, since localized attack gets caught before it becomes a through-wall leak.
• It also fits naturally alongside other corrosion and metallurgical testing already in a program, minimizing added complexity.