Measuring Iron (Fe) in Water: Why Can This Common Metal Disable Industrial Equipment?

Introduction: Is Brown Water Just a Visual Problem?

If your water is brown, has rusty stains on your dishes, or your pipes are clogged, your water probably has high levels of iron (Fe).

Many people think that iron is just an aesthetic problem.

But the reality is that dissolved iron in water can:

• Create hard deposits in boilers and chillers
• Initiate substrate corrosion
• Reduce heat exchanger efficiency by up to 40%
• Multiply maintenance costs

In this article, we will see why accurate iron (Fe) measurement is not an option, but a necessity for any industrial unit, power plant, or water circulation system.

What is iron (Fe) and why is it important in water?

Iron (Fe), with atomic number 26, is the most widely used metal in the world.

In nature, it is found in the form of minerals such as hematite, magnetite and pyrite, and is the main basis of steel and industrial alloys.

But this valuable metal can become a hidden enemy when it enters water as a dissolved ion.

Two chemical states of iron in water: Fe²⁺and Fe³⁺

Iron exists in water in two main forms:

1. Divalent iron (Fe²⁺)—“ferrous”

• Stable in oxygen-free waters (such as groundwater)
• It is colorless and soluble — so it is not visible to the eye
• But upon contact with air, it turns into Fe³⁺

2. Trivalent iron (Fe³⁺)—“ferric”

• Forms in the presence of oxygen
• It is insoluble and forms hydrated iron oxide (red rust)
• This compound is the same red deposit seen in pipes and equipment

Problems caused by high iron in water

1. Impact on water quality

• Brown or yellow color
• Unpleasant metallic taste
• Closure in drinking or process water

2. Impact on industrial equipment

• Formation of deposits in pipes, boilers, chillers and heat exchangers
• Reduced water flow and increased pump pressure
• Insulation Thermal → Reduction in efficiency up to 40%
• Electrochemical corrosion in circulating systems

3. Impact on production processes

• In the paper industry: brown spots on the final product
• In the leather industry: change in color and quality of the skin
• In ice making: cloudy and unsuitable ice

How does iron cause corrosion?

Corrosion of iron is an electrochemical process known as rusting.

Corrosion Mechanism:

1. Iron (Fe) loses electrons (oxidizes) in the presence of water and oxygen

2. Fe²⁺ ions are formed

3. These ions react with oxygen and water to form hydrated iron oxide (Fe₂O₃·nH₂O)

4. This combination forms a loose, porous layer that accelerates corrosion

Critical Note: In boilers and steam boilers, iron corrosion is more severe when:

• Water alkalinity is low
• Oxygen dissolved in water is present
• Temperature and mechanical stress are high

Iron corrosion in industrial equipment — a result of lack of control of Fe in water

Why is iron (Fe) measurement necessary?

Without accurate measurement, you cannot:

• Determine whether iron is dissolved or precipitated
• Identify the type of sediment (ferrous or carbonate?)
• Choose the appropriate descaling method
• Prevent secondary corrosion

Therefore, iron (Fe) analysis is the first step in any smart water management program.

Methods for measuring iron in water

Standard method: spectrophotometry with orthophenone trifluoromethyl

This method is the most accurate and widely used method for measuring iron in water.

Steps:

1. Water sampling (preferably without contact with air)

2. Reduction of trivalent iron: By adding hydroxylamine, all Fe³⁺ is converted to Fe²⁺

3. Color reaction: Fe²⁺ reacts with orthophena-netruline and forms a pink complex

4. Measurement of light absorption: With a spectrophotometer at a wavelength of 510 nm

5. Determination of concentration: Using a standard calibration curve

Permissible levels of iron in water (based on standards)

Warning: Even concentrations as low as 1 ppm can build up a thick layer of scale after a few months.

Frequently Asked Questions About Iron in Water

Does water filtration remove iron?

Conventional filters only remove solid particles, not dissolved iron (Fe²⁺).

To remove dissolved iron, you need oxidation + filtration or ion exchange.

Why does iron scale re-form after chemical washing?

Because the source of iron (such as feed water or internal corrosion) is still active.

Without controlling the source, scale will inevitably recur.

Can corrosion inhibitors be used to control iron?

Yes, but only if the iron concentration is controlled.

At high concentrations, corrosion inhibitors cannot prevent scale formation.

Practical Solutions for Iron Control in Industrial Systems

1. Source Control

• Regularly Analyze Feedwater
• Use Oxidation Filters to Remove Iron Before It Enters the System

2. Continuous Monitoring

• Periodic Measurement of Total and Dissolved Iron
• Monitor pH, Dissolved Oxygen, and Alkalinity

3. Smart Descaling

• Use Iron-Selective Descalers (Not General Acids)
• Include Corrosion Inhibitors to Protect Steel

4. Preventive Maintenance

• Periodic Flushing Before Thick Films Form
• Use Nitrogen Gas to Prevent Water from Contacting Oxygen During Idle Periods

Conclusion: Iron, a Friend That Becomes an Enemy in Water

Iron is a valuable metal — but in water, a hidden danger.

Without accurate measurement and smart planning, this common element can:

• Kill your equipment
• Multiply your costs
• Reduce the useful life of your systems

Is your equipment suffering from red scale, reduced efficiency, or corrosion?

By performing a comprehensive iron (Fe) analysis, identify the root cause of the problem and receive a safe and effective solution.

You can contact our experts for a free consultation.