Corrosion Testing

Corrosion Testing for Building Materials: Methods, Standards and Why it Matters

Steel inside a concrete slab, a painted steel frame, an aluminium cladding panel: all of them start life in good condition, and all of them are slowly attacked by the air, moisture and salts around them. Corrosion is hard to spot because much of the damage happens out of sight, under paint or inside concrete, long before a stain or a crack appears. In the Gulf, where coastal air, humidity, high temperatures and salty ground conditions all speed it up, buildings face this risk from the day they are finished. 

At METS Laboratories, we carry out corrosion testing on building and construction materials, so that contractors, consultants and owners can check how well a material will hold up before it is built in, and find out why it failed if it already has.

What is Corrosion Testing?

Corrosion is the gradual destruction of a material through a chemical or electrochemical reaction with its surroundings. Rusting of iron is the best-known example, but metals are not the only materials affected, and polymers and ceramics can also break down.

Corrosion testing measures how a material reacts to a corrosive setting, such as salt water, chemicals or damp air, and how well any coating protects it. It is one part of construction materials testing, also called building materials testing, which is a vital step in any infrastructure project. It checks that materials such as concrete, steel, asphalt, aggregates, soil and coatings meet Qatar Construction Specifications (QCS) and international standards such as ASTM, BS, ISO and EN.

Importance of Corrosion Testing of Building Materials 

A building is meant to last for decades, and corrosion is one of the main things that cuts that life short.

• Hidden damage: corrosion often starts where nobody can see it, such as on reinforcing steel inside concrete.
• Cracking and spalling: rust takes up several times the space of the steel it came from, so it pushes the concrete cover off the bar and exposes it to even more attack.
• Loss of strength: as steel thins, it carries less load, and structural safety falls with it.
• Harsh local conditions: chlorides from sea air and salty groundwater, sulphates in soil, and high heat and humidity all raise the risk in this region.
• Repair costs: repairing corroded concrete and steel is far more expensive than checking materials and coatings at the start.
• Specification checks: engineers set corrosion limits and coating requirements, and test results show whether the supplied material meets them.

Building Materials That Require Corrosion Testing

Any material in a damp, salty, or chemical environment can be a candidate.

• Reinforcing and structural steel: rebar, beams, columns, bolts and anchors.
• Concrete: its chloride content and its resistance to sulphate attack decide how well it protects the steel inside.
• Stainless steel: handrails, cladding, fixings and pipes, where poor heat treatment or welding can cause trouble.
• Coated and painted metal: steel frames, roofing, doors and facade systems that depend on a protective layer.
• Aluminium and composite panels: cladding and panels exposed to weather and pollution.
• Pipes, tanks and fittings: water and drainage systems that corrode from the inside.

What are the Different Corrosion Testing Methods?

The right method depends on the material, the environment it will face and what you need to know. These are the main methods in use at METS Laboratories.

Salt Spray Testing (ASTM B117)

Salt spray testing, commonly known as salt fog testing, is one of the oldest and most widely used methods for evaluating corrosion resistance. 

• How it works: samples sit in a closed chamber and are exposed to a fine mist of salt water for a set number of hours.
• What it tests: painted, coated, galvanized and bare metals, in marine-like conditions.
• What it is good for: comparing coatings or materials and ranking them against each other quickly.
• What it does not do: it does not give an exact number of years of life, so treat the result as a comparison.

Stainless Steel Testing (ASTM A262)

Stainless steel can lose its corrosion resistance if it is heated in the wrong way.

• Sensitization: improper heating, for example during welding, forms chromium carbides at the grain boundaries.
• Intergranular corrosion: the sensitised areas then corrode along those boundaries. ASTM A262 is the method used to check for this in austenitic stainless steel.

Hydrogen-Related Cracking

Some steels crack when hydrogen enters the metal.

• Hydrogen embrittlement: hydrogen diffuses into steel and makes it brittle, which matters for high-strength bolts and fasteners.
• Hydrogen induced cracking (HIC): tested to NACE TM0284 and to the requirements of NACE MR0175.

Concrete Testing for Chloride and Sulphate

Concrete protects the steel inside it, but chlorides and sulphates can break that protection down.

• Chloride content: high chloride levels can start rusting on the reinforcing steel. [confirm METS method]
• Sulphate attack: sulphates react with the cement paste and damage the concrete itself.

Coating Evaluation

Coatings are often the first line of defense, so they need checking too.

• Thickness: dry film thickness is measured on ferrous and nonferrous metals (ASTM D7091).
• Salt spray ranking: coatings are compared by how well they resist the chamber.
• Electrochemical evaluation: tests on the material or coating to see how it behaves in a corrosive setting.

Failure Analysis

Failure analysis studies a component that has already failed, to find the root cause and stop it happening again.

• Remaining wall thickness: measured in pipes, tubes and tanks that may be corroding from the inside.
• Root cause: the investigation finds the mechanism, such as pitting, cracking or fatigue.
• Forensic work: used after a leak, fire or chemical accident to assess damage to metal parts.

Corrosion Testing Process

The process is the same in outline for most materials.

1. Briefing: you tell us the material, where it will be used and what standard or specification applies.
2. Preparation: the sample is cleaned, measured and, where needed, cut or masked to the shape the test calls for.
3. Exposure or measurement: the sample goes into the test, such as a salt spray chamber, or is measured directly.
4. Inspection and rating: we check for rust, blistering, cracking or mass loss and rate it against the method.
5. Reporting: the results are written up against your specification.

Who Needs Corrosion Testing?

Anyone who specifies, supplies or looks after building materials can use the results.

• Main contractors and subcontractors
• Consultants and project engineers
• Developers and facility managers
• Manufacturers of steel, coatings and cladding
• Inspection and quality assurance teams

Why Choose METS as Corrosion Testing Laboratory?

Corrosion work is part chemistry and part detective work, so here is what matters for this test.

• A dedicated corrosion and failure analysis team: one specialist service for both prevention and investigation.
• Salt spray and beyond: salt fog testing (ASTM B117), stainless steel intergranular corrosion checks (ASTM A262) and hydrogen cracking tests (NACE TM0284, NACE MR0175).
• Life estimates: electrochemical and coating evaluation to compare materials and estimate how long they will last.
• Root-cause investigation: we find out why corrosion happened, including remaining wall thickness in pipes and tanks.

At METS Lab, our ISO/IEC 17025-accredited facility tests building materials for quality, durability, and compliance with UAE’s construction and engineering standards.

Conclusion

Corrosion is slow, quiet and expensive, and in this region it has plenty to work with. Corrosion testing shows how steel, concrete, coatings and fittings will cope before they are built in, and failure analysis explains what went wrong when they do not. If you have materials to check or a corroded component to investigate, send METS Laboratories the material details, the specification and the test you need, and our team will advise on the next step.

Frequently Asked Questions

1. Why is corrosion of rebar such a problem in concrete? 

Ans: Concrete normally keeps steel protected, but chlorides or carbonation can break that protection down. The rust that forms takes up more space than the steel, so it cracks the concrete and lets more moisture in.

2. Does passing a salt spray test mean a coating will last for years? 

Ans: Not by itself. Salt spray is a quick way to compare coatings, but real life has sunlight, heat, rain and wear, so the result is a guide and not a guarantee.

3. What is the difference between corrosion testing and failure analysis? 

Ans: Corrosion testing checks how a material is likely to behave. Failure analysis starts with a part that has already failed and works out why.

4. What is an ASTM corrosion test?

Ans: It’s a lab method published by ASTM International that shows how a material reacts to a corrosive environment, using set steps so results can be compared. There isn’t just one. Different ASTM standards cover different jobs. ASTM B117 is salt spray testing for coatings and metals, and ASTM A262 checks stainless steel for intergranular corrosion.