ASTM G46 Examination and Evaluation of Pitting Corrosion

ASTM G46 explains how to choose from a variety of ways for examining and evaluating pitted metals. Both nondestructive and destructive methods are used in these operations. The values stated in SI should be considered as standard.

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ASTM G46 Examination and Evaluation of Pitting Corrosion

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Overview
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

ASTM G46 is used to examine and evaluate pitting corrosion in metallic materials. The test provides methods for identifying, measuring, and characterizing pits formed on metal surfaces due to localized corrosion.

This method is widely applied in corrosion studies, failure analysis, and material performance evaluation. It helps engineers assess the severity of pitting, understand corrosion mechanisms, and determine the suitability of materials for corrosive environments.

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:

Depth of corrosion pits on metal surfaces
Density and distribution of pits
Severity of localized corrosion damage
Surface condition after corrosion exposure
Corrosion behavior of metallic materials

Applications

Corrosion testing of metals and alloys
Oil and gas industry components
Marine and offshore structures
Chemical processing equipment
Aerospace and automotive materials
Failure analysis and material evaluation

Benefits

Provides a standardized evaluation of pitting corrosion
Helps assess the severity of localized corrosion damage
Supports material selection for corrosive environments
Assists in failure analysis and root cause investigation
Enables comparison of corrosion resistance between materials

Test Process

Sample Preparation

Corroded specimens are cleaned to remove corrosion products without altering pit geometry.

Surface Examination

The surface is visually and microscopically examined to identify pits.

Pit Measurement

Pit depth, size, and distribution are measured using appropriate techniques.

Data Recording & Evaluation

The measured data is analyzed to assess pitting severity and corrosion behavior.

Technical Specifications

Parameter	Details
Applicable Materials	Metals and alloys
Pit Depth Range	~1 µm to 5 mm
Pit Diameter Range	~10 µm to 10 mm
Measurement Resolution	Up to 0.1 µm (microscopy/profilometry)
Magnification Range	10× to 500×
Evaluation Criteria	Pit depth, density (pits/cm²), and distribution

Instrumentation Used for Testing

Optical microscope (10×–500×)
Surface profilometer (resolution up to 0.1 µm)
Measuring microscope or depth gauge
Sample cleaning equipment (chemical/ultrasonic)
Image analysis software
Data acquisition system

Results and Deliverables

Pit depth and diameter measurements
Pit density (pits/cm²) data
Corrosion severity classification
Surface morphology analysis
Test condition summary
ASTM compliance report

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Frequently Asked Questions

ASTM G46 includes pit depth measurement, pit density, pit distribution, surface area affected, and metallographic examination, evaluating severity of pitting corrosion and providing quantitative and qualitative assessment of localized corrosion damage.

ASTM G46 uses visual inspection, optical microscopy, profilometry, and metallographic techniques to measure pit characteristics and assess corrosion damage on metal surfaces.

ASTM G46 is commonly applied to metals and alloys such as stainless steels, aluminum alloys, and other corrosion-resistant materials exposed to aggressive environments.

ASTM G46 evaluates pit size, depth, density, and distribution, providing data to assess corrosion severity and predict potential impact on structural integrity.

ASTM G46 evaluates pitting corrosion after exposure and does not predict initiation mechanisms, requiring additional testing to understand environmental factors and long-term corrosion behavior.