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.
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Corrosion rate by mass loss
The mass loss method (weight loss) is the oldest, simplest and most reliable way to measure corrosion: a clean coupon gets weighed, exposed to the aggressive medium for a known period, then carefully stripped of corrosion products and weighed again. The difference is the corroded mass. The corrosion rate converts that loss into a uniform penetration velocity: CR = 87.6 × W ÷ (D × A × t), with W in mg, density D in g/cm³, exposed area A in cm², time t in hours and the result in mm/year (the constant 87.6 handles the unit conversion). Expressing corrosion as penetration per year is what lets the engineer size the equipment: a corrosion allowance gets defined, extra wall thickness that will be consumed over the expected service life of the equipment. As a reference, rates below ~0.1 mm/year generally count as good resistance; above ~1 mm/year, the material suits few applications. One caveat: this rate assumes uniform corrosion; localised forms (pitting, crevice attack) can perforate much faster with only a small mass loss. Enter the mass loss, the density, the area and the 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.
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.
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.
Bearing Life L10
Compute nominal bearing life L10 in million revs: L10 = (C/P)^p with p=3 (ball) or p=10/3 (roller).
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.
Electrochemical Equivalent Weight
Calculate the electrochemical equivalent weight, EW = M ÷ n, dividing the element's molar mass M (g/mol) by the number of electrons exchanged n (valence). The result, in g/eq, is the mass associated with transferring one mole of electrons and appears in nearly every electrochemical calculation: Faraday's law, electrochemical corrosion rate, electrodeposition and anode sizing. For divalent iron (Fe²⁺), for example, EW = 55.85 ÷ 2 ≈ 27.9 g/eq. Enter the molar mass and the number of electrons exchanged.
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