A piece of corroded steel plate was found in a submerged ocean vessel. It was estimated that the original area of the plate was 16 in. 2 and that approximately 3.2 kg had corroded away during the submersion. Assuming a corrosion penetration rate of 200 mpy for this alloy in seawater, estimate the time of submersion in years. The density of steel is 7.9 g/cm3.

Question

Paige

Engineering

7 January, 10:13

A piece of corroded steel plate was found in a submerged ocean vessel. It was estimated that the original area of the plate was 16 in. 2 and that approximately 3.2 kg had corroded away during the submersion. Assuming a corrosion penetration rate of 200 mpy for this alloy in seawater, estimate the time of submersion in years. The density of steel is 7.9 g/cm3.

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Israel · Answer 1

Time of submersion in years = 7.71 years

Explanation:

Area of plate (A) = 16in²

Mass corroded away = Weight Loss (W) = 3.2 kg = 3.2 x 106

Corrosion Penetration Rate (CPR) = 200mpy

Density of steel (D) = 7.9g/cm³

Constant = 534

The expression for the corrosion penetration rate is

Corrosion Penetration Rate = Constant x Total Weight Loss/Time taken for Weight Loss x Exposed Surface Area x Density of the Metal

Re - arrange the equation for time taken

T = k x W / A x CPR x D

T = (534 x 3.2 x 106) / (16 x 7.9 x 200)

T = 67594.93 hours

Convert hours into years by

T = 67594.93 x (1year/365 days x 24 hours x 1 day)

T = 7.71 years