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🧂 Chloride Service Life Explorer
Most concrete structures don't fail structurally — they corrode out of service decades earlier. Chloride from seawater or de-icing salt diffuses slowly inward until it reaches the reinforcement and strips its passive film. Change the cover, the mix quality, and the exposure, and watch the initiation clock move.
Exposure
Concrete
Lower D = denser, better-cured concrete or supplementary binders. Published values span orders of magnitude — this is an input, not a built-in assumption.
Time
Live Result
Chloride at reinforcement now—
Time to corrosion initiation—
Status at the age shown—
Powered by the error-function solution to Fick's
second law (
engine/chloride-diffusion.js). Verified before
publishing against an independent numerical finite-difference solution of
the diffusion PDE — agreement to about seven decimal places, which checks
that the engine genuinely solves the diffusion equation rather than merely
reproducing a transcribed formula. The initiation time is also round-trip
verified: feeding it back into the concentration equation returns Ccrit
exactly. Try doubling the cover and watch initiation time quadruple — the
cover² dependence is the cheapest durability lever a designer has.Method
Fick's 2nd lawC(x,t) = C₀ + (Cs−C₀)·[1 − erf(x/(2√(Dt)))] — semi-infinite medium, constant surface concentration.
erfAbramowitz & Stegun 7.1.26 rational approximation (~1.5×10⁻⁷); erfinv by Newton refinement.
Scope: constant D and Cs, saturated one-dimensional diffusion. Does not model time-dependent (ageing) D, the near-surface convection zone, carbonation interaction, chloride binding, or the propagation phase after initiation — this predicts when corrosion starts, not when the member fails.