Corrosion Thickness Loss
Calculate the cumulative thickness lost to corrosion, δ = CR × t, multiplying the corrosion rate CR (mm/year) by the service time t (years). The result, in mm, is the depth of material consumed over the period — direct input to assess the integrity of piping, tanks and structures and to decide on inspection, repair or replacement. Compared with the corrosion allowance set in design, it shows how much of the margin is already used and estimates the component's remaining life. Enter the corrosion rate and the service time.
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Corrosion thickness loss
Once the corrosion rate of a material in a given environment is known, the next practical question is how much wall it has already lost (or will lose) over time. The answer is a straight multiplication: δ = CR × t, the corrosion rate (mm/year) times the service time (years), giving the depth of material consumed in mm. That figure underpins the integrity assessment of equipment. When designing a pressure vessel or a piping run, a corrosion allowance is added to the minimum structural thickness, computed precisely as CR × design life. In service, ultrasonic thickness readings compare the accumulated real loss against that margin: if the loss has already eaten a good share of the allowance, the remaining life is computed ((current thickness − minimum) ÷ CR) and the choice is made between tightening the inspection, derating the operating pressure, repairing or replacing the component. The calculation assumes a constant and uniform corrosion rate; in environments that vary, or with localized attack, the most conservative measured rate is used. Enter the corrosion rate and the service time.
Related Tools
Thickness with Corrosion Allowance
Calculate the total thickness to specify for a pressure-vessel component including the corrosion allowance, t_total = t_calculated + CA, from the minimum pressure-calculated thickness t_calculated (mm) and the corrosion allowance CA (mm). The thickness from the ASME formulas is the MINIMUM needed to resist pressure — but the vessel will operate for DECADES, and corrosion (and erosion) will consume wall material over time. If the vessel were made exactly at the minimum thickness, the first corrosion would already leave it below safe. So a CORROSION ALLOWANCE (CA) is added — a 'sacrificial' over-thickness, typically 1.5 to 6 mm, sized for the expected corrosion rate times the design life (e.g., 0.1 mm/year × 25 years = 2.5 mm). Thus the thickness specified for fabrication is the structural minimum plus the corrosion allowance. Over life, inspection (by ultrasound) measures the REMAINING thickness; when corrosion consumes the whole allowance and the thickness approaches the structural minimum, the vessel must be repaired or retired. The corrosion allowance is like a 'life reserve' built into the wall. Enter the calculated thickness and the corrosion allowance.
Corrosion Rate (Mass Loss)
Calculate the corrosion rate by the mass-loss method, CR = 87.6 × W ÷ (D × A × t), from the mass loss W (mg), the material density D (g/cm³), the exposed area A (cm²) and the exposure time t (hours). The result, in mm/year, is the average speed at which the metal is consumed by corrosion — the key parameter to predict the service life of structures, piping and equipment and to set the corrosion allowance in design. Rates below 0.1 mm/year are usually acceptable. Enter the mass loss, density, area and time.
Sacrificial Anode Life
Calculate the life of a sacrificial anode, life = (mass × capacity) ÷ (current × 8760), from the anode mass (kg), the material's current capacity (A·h/kg), the protection current drained (A) and the 8760 hours in a year. The result, in years, shows how long the anode (zinc, aluminium or magnesium) will provide protection before being consumed and needing replacement — essential in designing galvanic cathodic protection of tanks, pipelines and marine structures. Enter the mass, the material capacity and the current.
Larson-Skold Index (Water Corrosivity)
Computes the Larson-Skold index, the ratio between the aggressive and the protective anions in a water: chloride plus sulphate divided by alkalinity, all converted to milliequivalents per litre with the equivalent weights 35.45 for chloride, 48.03 for sulphate and 50.04 for alkalinity expressed as CaCO₃. The reading is direct: below 0.8 alkalinity dominates and the carbonate film protects carbon steel; between 0.8 and 1.2 corrosion stops being negligible; above 1.2 chloride and sulphate break the film and the localised corrosion rate takes off, the typical scenario of cooling tower makeup water running at many cycles of concentration. Unlike the Langelier index, this one does not say whether the water will scale — it measures only the corrosive power of the anions, which is why the two readings complement each other rather than compete. Total alkalinity was adopted as the input, instead of separate bicarbonate and carbonate, because that is what a routine laboratory reports, and converting it through the CaCO₃ equivalent returns exactly the sum of the two in milliequivalents per litre. Enter the chloride, the sulphate and the total alkalinity.
Pipe Pressure Loss Calculator
Pipe head loss via Hazen-Williams: J = 10.67 × Q^1.85 / (C^1.85 × D^4.87). For water at 20°C.
Corrosion Inhibitor Efficiency
Calculate the efficiency of a corrosion inhibitor, η = (CR₀ − CR_inh) ÷ CR₀ × 100%, comparing the corrosion rate without inhibitor (CR₀) with the rate in its presence (CR_inh). The result, in %, measures how much the inhibitor slowed corrosion — the standard indicator to evaluate and compare inhibitors in laboratory tests (mass loss, polarization or impedance). Effective inhibitors form protective films on the surface and reach efficiencies above 90%. It is widely used in boiler water treatment, cooling systems and well acidizing. Enter the corrosion rates without and with inhibitor.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.