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.
Result
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Vida útil de ânodo de sacrifício
Num sistema de proteção catódica galvânica, o metal a proteger é ligado a um ânodo de sacrifício — um metal menos nobre (zinco, alumínio ou magnésio) que se corrói no lugar da estrutura, fornecendo a corrente de proteção enquanto se consome. Como o ânodo é uma peça que se gasta, é essencial estimar sua vida útil para planejar a substituição: vida = (massa × capacidade) ÷ (corrente × 8760). A capacidade de corrente (A·h/kg) é uma propriedade do material do ânodo — quanto de carga elétrica cada quilo é capaz de fornecer antes de se esgotar (o zinco fornece da ordem de 780 A·h/kg, o alumínio bem mais, ~2000, o magnésio ~1230). Multiplicada pela massa do ânodo, dá a carga total disponível (A·h); dividida pela corrente drenada (A) e pelas 8760 horas do ano, resulta na vida em anos. Na prática aplica-se ainda um fator de utilização (tipicamente 0,8–0,9), pois o ânodo não pode ser consumido 100% (os pedaços finais se desprendem). Dimensionar a massa de ânodos para cobrir toda a vida de projeto da estrutura — ou prever paradas de troca — é parte central do projeto de proteção catódica de tanques, dutos e estruturas marinhas. Informe a massa, a capacidade do material e a corrente.
Related Tools
Cathodic Protection Current
Calculate the current needed for cathodic protection, I = current density × area ÷ 1000, multiplying the required protection current density (mA/m²) by the metal surface area to protect (m²). The result, in amperes, sizes cathodic protection systems — impressed current or sacrificial anodes — that protect pipelines, buried tanks, ship hulls and offshore structures by polarizing the metal to a corrosion-immune potential. The required density depends on the medium and the coating. Enter the protection current density and the area to protect.
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.
Reservoir Life (Sedimentation)
Estimate a reservoir's useful life from sedimentation, Vu = V ÷ V_s, from the reservoir's useful (or total) volume V (m³) and the sediment volume deposited per year V_s (m³/year). Every reservoir, by impounding a river, slows the flow and makes water lose its sediment-carrying capacity — sand, silt and clay from the watershed settle on the bottom, gradually reducing storage. The useful life is the number of years until sedimentation impairs the reservoir's function (power, supply, regulation). It is a crucial design parameter in hydrology and watershed management: reservoirs in basins with erodible soils, deforestation or intensive agriculture silt up fast (decades), while well-conserved basins last centuries. The sediment inflow V_s comes from the basin's sediment yield and the reservoir's trap efficiency (Brune curve). The simple constant-rate model gives the order of magnitude. Conserving the basin and flushing through bottom outlets extend the life. Enter the reservoir volume and the annual sediment inflow.
Tafel Overpotential
Calculate the activation overpotential by the Tafel equation, η = a + b × log₁₀(i), from the Tafel constant a (V), the Tafel slope b (V/decade) and the current density i. The result, in volts, is the overpotential — how far an electrode's potential departs from equilibrium — needed to sustain a given current density in an activation-controlled electrochemical reaction. The Tafel relation is central to electrode kinetics, corrosion (extrapolation to obtain the corrosion current) and electrolysis. Enter the Tafel constant, slope and current density.
L10 Life in Hours (Bearing)
Calculate a bearing's nominal L10 life in HOURS of operation, L10h = (10⁶ ÷ (60·n))·(C/P)^p, from the dynamic load rating C (N), the equivalent dynamic load P (N), the rotation n (rpm) and the exponent p (3 for ball bearings, 10/3 for roller bearings). L10 life is the core of bearing selection: the number of revolutions (or hours) that 90% of a batch of identical bearings reaches or exceeds before FATIGUE failure (spalling of races and rolling elements) — i.e., only 10% fail earlier (hence 'L10', the life with 90% reliability). The basic formula L10 = (C/P)^p gives life in MILLIONS of revolutions; dividing by the rotation (rpm × 60 min/h) converts to hours, the practical unit for machines. The result shows the huge load sensitivity: since the exponent is 3 (balls), DOUBLING the load cuts life to 1/8! So a slightly overloaded bearing lasts far less. The capacity C is tabulated in each bearing's catalog. This calculation decides whether a bearing meets the application's required life (typically 20,000-100,000 h for industrial machines) or whether a larger one is needed. Enter the dynamic capacity, the equivalent load, the rotation and the exponent.
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