Question

A piece of corroded steel plate was found in submerged ocean vessel. It was estimated that the area of plate to be ~38 inch 2, and weight loss due to corrosion was 1.9 Kg. Assuming a corrosion rate of 120 mpy for this steel in seawater, estimate the of submersion time in years for this steel plate?

Answer 1

Answer:

3.2 years

Explanation:

The corrosion penetration rate (CPR) is given by:

$CPR=\frac{KW}{\rho At} \\\\Where:\\K=constant, W=weight\ loss, \rho=density\ of\ specimen, A=area\ of\ exposed\ specimen, t=time\ exposed$

Given that:

CPR = 120 mpy, W = 1.9 kg = 1900 g, density of steel = 7.9 g/cm³, A = 38 in², K = 534 (for 10⁻³ in per year),

Substituting:

$120 \ mpy=\frac{534*1900\ g*(10^3\ mg/g)}{7.9g/cm^3*38\ in^2*t} \\\\t=\frac{534*1900\ g*(10^3\ mg/g)}{7.9g/cm^3*38\ in^2*120\ mpy} \\\\t= 28164.56\ hours\\\\t=\frac{28164.56\ hours}{24\ hr/day*365\ day/year}\\\\t= 3.2 \ years$