Corrosion analysis of metal powders: identifying the source

Une problématique de corrosion sur poudres métalliques peut avoir plusieurs origines : contamination particulaire, oxydation de surface, présence d’agents corrosifs, hétérogénéité matière, dérive de composition chimique ou conditions de stockage et de recyclage inadaptées. Dans les secteurs de la métallurgie et de la fabrication additive, ces phénomènes peuvent dégrader la coulabilité, modifier la réactivité de surface, favoriser les inclusions et impacter la tenue finale des pièces. L’enjeu est donc de remonter rapidement à l’origine corrosion afin de distinguer un défaut matière, un défaut de procédé ou une contamination externe. Pour approfondir les enjeux liés aux poudres en fabrication additive, consultez notre page dédiée à la caractérisation des poudres métalliques et notre contenu sur la fabrication additive de pièces métalliques.

The investigation begins with observing the powder morphology or degraded surfaces: surface condition, porosity, irregularities, cracks, wear, inclusions, deposits, or oxidized areas. In the event of part failure, fractographic analysis makes it possible to characterize the fracture mode, whether brittle, ductile, or fatigue-related, and then look for signs of corrosive attack. Optical microscopy, SEM-EDX, FE-SEM, and, depending on requirements, X-ray tomography make it possible to visualize defects and locate the areas to be analyzed.

The investigations rely on complementary methods: SEM-EDX for morphology and local composition, optical microscopy for metallographic observations, a hardness tester for hardness comparisons, ICP for composition analysis, elemental analyzers C/S, N/O, and H for gas and light element control, XRD for phase identification and crystalline impurities, as well as XPS for extreme-surface chemistry. For powders, checks of particle size distribution, density, flowability, moisture, and morphology complete the investigation. In addition, our expertise in powder rheology analysis can help link surface condition to flow behavior.

Using an expert laboratory saves time in identifying root causes: batch contamination, grade drift, abnormal oxidation, inclusion, surface defect, or process/material incompatibility. The goal is not only to observe corrosion, but to connect analytical findings to an industrial decision: accept or block a batch, adjust a manufacturing parameter, review storage, qualify a supplier, or correct a surface treatment.

An expert laboratory supports manufacturers in determining the origin of a failure through a multi-technique, multi-scale approach. The investigation may include surface examination, identification of corrosion products, verification of metal grades, impurity screening, elemental composition analysis, and comparison between conforming and non-conforming batches. This approach makes it possible to validate the resistance of materials and surface treatments, anticipate risks before industrialization, and make powder qualification, production, or recycling stages more reliable.

To understand a corrosion analysis, it is necessary to determine the chemical nature of the species present on the surface and within the bulk. analysis by ICP-AES, ICP-MS, elemental analysis C/S, N/O, H, XRD, and XPS make it possible to verify the alloy composition, detect trace elements, highlight crystalline impurities, and identify oxidation or passivation states. This approach is particularly useful for comparing the powder against specifications, verifying a metal grade, or searching for an oxidizing or corrosive agent.

When the objective is to validate the resistance of a material or coating, electrochemical tests can be carried out: open-circuit potential (OCV) measurement, corrosion rate by LSV, electrochemical impedance spectroscopy (EIS), and galvanic coupling studies. Accelerated aging and salt spray tests also make it possible to assess corrosion resistance, the homogeneity of a surface treatment, and the thickness loss of a coating. These data are useful both in failure analysis and in process qualification.

This expertise is also strategic for additive manufacturing, where powder stability determines process repeatability and the final performance of parts. A comparative study between batches, recycling monitoring, or initial characterization makes it possible to anticipate drifts before they affect production. Manufacturers can also build their expertise through training on metal powder analysis tailored to their technical challenges.

To start an expert assessment, it is necessary to specify the context in which the defect appeared, the type of powder or alloy involved, the storage or recycling history, the expected specifications, and, if possible, reference batches. The study can then be structured around observation, chemical analysis, surface characterization, batch-to-batch comparison, and interpretation of the results in light of the industrial process. This approach makes it possible to reach a well-supported conclusion on the corrosion origin and on the actions to be taken.