How can you prove that corrosion is linked to water quality?

Corrosion observed on a pipe, heat exchanger, storage tank or DHW system cannot be attributed to the mere presence of water.

To demonstrate a causal link, water must be characterized as a living chemical reactant: pH, alkalinity, hardness, mineral content, dissolved gases, chlorides, sulfates, bicarbonate/calcium ratio, oxidation-reduction potential and any presence of inhibitors or contaminants. The analysis must also take into account the calco-carbonic balance, scaling or aggressive tendency, the Langelier index, the Larson index and the actual hydraulic context. Ignoring water composition means accepting the programmed deterioration of your installations.

The water aggressiveness analysis begins with measuring the main parameters: pH, conductivity, alkalinity, total alkalinity, total hardness, calcium, magnesium, bicarbonates, chlorides, sulfates, silica, dissolved oxygen, free CO2 and temperature.

Depending on the case, additional investigations focus on dissolved metals, halogens, corrosion inhibitors, oxidizing agents and exogenous contaminants. Calculating the Langelier index helps assess calco-carbonic stability, while the Larson index highlights the corrosive risk linked to the ratio between aggressive anions and protective alkalinity.

Examining the component makes it possible to identify the attack mode: pitting corrosion, crevice corrosion, galvanic corrosion, under-deposit corrosion, erosion-corrosion or generalized oxidation. Surface and cross-section observations, combined with chemical analysis of deposits and corrosion products, often reveal precursors such as chlorides, contaminants, coating heterogeneities or localized defects.

This step makes it possible to determine whether the morphology of the attack is consistent with the action of the aqueous environment.

La démonstration s’appuie sur des moyens complémentaires : analyses élémentaires par ICP, observations métallographiques, microscopie optique et microscopie électronique, analyses de surface par XPS, identification de phases par DRX, caractérisation morphologique et chimique des dépôts par MEB-EDX.

À cela s’ajoutent des essais électrochimiques tels que potentiel libre OCV, vitesse de corrosion LSV, impédance électrochimique EIS et étude de couplage galvanique pour quantifier le comportement du matériau dans un milieu représentatif.

The proof is not based on a hypothesis but on a set of consistent indicators: the nature of the corrosion mode, the composition of the deposits, the chemical signature of the water, material/environment compatibility, corrosion rate and operating history.

A structured laboratory report makes it possible to distinguish freshwater corrosion, under-deposit corrosion, chloride-induced pitting, galvanic coupling or a failure related to installation.

This approach is decisive for system operators, property managers, insurers, engineering consultants and pipe manufacturers seeking to objectively assign responsibility between the water supplier, installer and manufacturer.

Poorly mineralized water, water that is unbalanced in calco-carbonic terms, or water enriched with chlorides and sulfates can dissolve protective films, promote pitting or accelerate generalized corrosion.

Conversely, scaling water can mask or shift the mechanisms by creating deposits beneath which localized attack develops. Interpretation therefore cannot be limited to a single value: it requires a global reading of the environment, the material and the operating conditions.

Establishing responsibility then requires comparing these results with the metal grade, metallurgical condition, surface treatment, assemblies, material pairings and installation conditions. Aggressive water may be the main cause, an aggravating factor or simply a revealer of a design weakness.

Only a combined expert assessment can distinguish a material nonconformity, an installation defect, a poor material choice or water that is chemically unsuitable for the system.

When necessary, simulations of specific environments make it possible to reproduce the real conditions: fresh water, highly chlorinated water, extreme pH, the presence of inhibitors or accelerated aging conditions. This experimental strategy turns a suspicion into technical proof. The final report brings together the findings, analytical results, mechanistic interpretation and the conclusion on the most likely origin of the corrosion.

FILAB acts as a trusted third party for cases where the evidence must be clear, documented, and defensible. The laboratory’s strength lies in combining metallurgy, water chemistry, and electrochemical testing, with surface, composition, and aging analysis capabilities tailored to construction and infrastructure network issues.

This approach makes it possible to determine the origin of corrosion with precision, to objectively establish responsibility, and to provide a laboratory report that can serve as a decisive technical document in an insurance, adversarial, or pre-litigation context. Analyze, compare, demonstrate, assign.