Corrosion testing
Corrosion damage can have serious consequences – from crippled production processes to the failure of entire systems. Systematic tests and methods are required during corrosion testing to prevent such failures.
Table of contents
What is corrosion?
Corrosion refers to the deterioration of metals caused by oxidation. During this process, materials are broken down by chemical or electrochemical reactions with their surroundings. The causes are numerous, however crucial factors are moisture, acids, salts as well as other environmental conditions. The consequence is the gradual destruction or degradation of the material.
What is corrosion testing?
Corrosion testing involves a series of tests and methods aimed at the evaluation of the resistance of materials to corrosive effects. These tests simulate different corrosive environments and exposures to determine the service life and reliability of materials and components. In this way potential weak spots can be identified and suitable measures taken to improve the corrosion resistance.
Corrosion testing
at Quality Analysis
We combine various microscopic methods in our accredited test laboratory to identify the exact causes of corrosion. In this way, a very wide range of materials and products can be analysed and potential corrosion damage prevented.
- Corrosion testing as part of destructive material testing
- Non-destructive testing of your component using industrial computed tomography
- Systematic damage analysis for the analysis of statically and dynamically loaded components and other physical damage
- Identification of corrosion mechanisms using light microscopy and scanning electron microscopy
Corrosion testing: detecting potential problems at an early stage
Corrosion testing plays a vital role in ensuring the quality and durability of materials and products. It permits the detection of corrosion problems at an early stage, the extension of the service life of products and the reduction of maintenance and replacement costs. It also improves safety, promotes compliance with regulations and standards, and contributes to the development of new materials.
Corrosion testing for cause analysis
Not all corrosion is the same. Depending on the ambient conditions and material, corrosion can have many causes. During corrosion testing, the type of corrosion is therefore determined to identify the specific cause of corrosion damage:
- Intercrystalline corrosion affects the grain boundaries in a metallic material while the grains are left largely unaffected. It often occurs in austenitic stainless steels. Important standards for the evaluation of material resistance include ASTM A262, ASTM G28 and DIN EN ISO 3651.
- Pitting and crevice corrosion are forms of corrosion in which minor pitting or cavities form on the metal surface. Pitting corrosion often occurs in environments containing chloride, crevice corrosion in joints, seals and at overlaps. Important standards during testing are ASTM G48, ISO 3651-2, ASTM G85 and DIN 50900.
- Stress corrosion cracking (SCC) occurs if a material is under mechanical stress and is exposed to a corrosive environment at the same time. It results in the formation of cracks in the material. The most important standards include ASTM G36, ASTM G47, ASTM G129, ISO 7539 and NACE TM0198.
- Hydrogen induced cracking (HIC) is particularly relevant in the oil and gas industry where hydrogen can penetrate materials and cause embrittlement and cracking. HIC is evaluated using special test methods described in standards such as NACE TM0284 and NACE TM0198.
Corrosion test methods
In practice, often both materialographic and chemical test methods are combined for testing corrosion resistance. Materialographic analyses provide assistance with understanding the physical effects of corrosion, while chemical tests identify the underlying chemical corrosion mechanism. There are numerous methods for corrosion testing, including the salt spray test, condensed water test, temperature change test and filiform test.
Chemical test methods
Chemical methods have an important role during corrosion testing, particularly during the analysis of chemical reactions that cause corrosion. Using gravimetric methods, the amount of material mass lost in corrosive conditions can be determined. By monitoring the pH value, the exposure of the samples to acids/bases can be determined. Ion chromatography (IC) helps with the determination of concentration of corrosive ions such as chloride and sulphate.
The chemical composition of samples can be analysed effectively using energy-dispersive X-ray spectroscopy (EDX). EDX utilises X-rays to identify and quantify the chemical elements in a sample. This method is often used to verify if there is contamination on the surface of samples, to identify foreign-matter inclusions in materials and to detect the finest traces of corrosion that are not visible to the naked eye.
Materialographic test methods
For the detailed analysis of wear and corrosion mechanisms, in materialography various microscopic methods are used that provide specific insights into the structure and composition of the samples. Light microscopy makes it possible, for instance, to analyse the surface structure and the nature of the corrosion at the microscopic level to obtain initial indications of the extent of the corrosion. In addition, scanning electron microscopy (SEM) provides high-resolution images of the surface morphology that can be examined in greater detail using energy-dispersive X-ray spectroscopy (EDX) to analyse the chemical composition of the corroded areas.
Applications for corrosion testing
Automotive
In the automotive industry, corrosion mechanisms are tested to ensure the safety, durability and quality of vehicles. These tests include checking the corrosion resistance of bodywork parts, suspension elements and other components potentially susceptible to corrosion.
Aerospace industry
Aircraft are subjected to extreme ambient conditions such as moisture, salt spray and temperature fluctuations that can accelerate corrosion. By means of regular corrosion testing, potential corrosion damage can be detected and rectified at an early stage to prevent failures and accidents.
Electronics manufacturing
Korrosion kann die Leistung von elektronischen Bauteilen beeinträchtigen und zu Ausfällen führen. Deshalb werden für die Elektronikindustrie elektronische Bauteile und Gehäuse auf ihre Beständigkeit gegenüber Korrosion in feuchten oder chemisch aggressiven Umgebungen getestet.
Battery cell analytics
Corrosion can degrade the performance and service life of battery cells. By means of comprehensive damage analysis in battery cell analytics, it is determined whether corrosion on battery cells was caused by external environment effects, incorrect manufacturing processes or material defects.
Summary: corrosion testing
Corrosion testing is an essential method for evaluating the corrosion resistance of materials and products. It includes various test procedures and test methods with the goal of simulating the behaviour of materials in corrosive environments, that is environments that cause long-term decay, and detecting potential weak spots.
