The weight loss of an aluminum alloy corroding in a solution of hydrochloric acid was observed to be 0.250 g/cm2 after an 8 h immersion period [13]. What is the corresponding anodic current density in milliamperes per square centimeter, assuming that all the corrosion is due to the following anodic half-cell reaction:

This question is incomplete, the complete question is;

The weight loss of an aluminum alloy corroding in a solution of hydrochloric acid was observed to be 0.250 g/cm² after an 8 h immersion period [13]. What is the corresponding anodic current density in milliamperes per square centimeter, assuming that all the corrosion is due to the following anodic half-cell reaction:

Al → Al³⁺ + 3e⁻

The atomic weight is 58.7 g/mol

Current density in milliamperes per square centimeter is 45.81 mA/cm²

Explanation:

Given the data in the question;

we know that Faradays law of electrolysis states that;

amount of substance produced at each electrode is directly proportional to the quantity of charge flowing through the cell.

so

m = ( Q/F) (M/z)

where m is the mass of substance liberated at an electrode( 0.250 g/cm²)

Q is the total electric charge passed through the substance

F is Faradays constant (96,500 C/mol)

M is the molar mass of the substance( 58.7 g/mol )  and Z is the number of electrons transferred(3)

Also

we know that; Q = It

where I is current and t is time( 8hrs × 60 × 60 = 28800 sec )

we substitute  Q = It  into our equation'

we have;

m = ( It/F) (M/z)

m = ItM / Fz

mFz = ItM

I = mFz / tM

so we substitute

I = [0.250 g/cm² × 96,500 C/mol × 3] / [ 28800 × 58.7 g/mol]

I = 72375 /  1690560

I = 0.04581 A/cm²

we know that; 1 ampere = 1000 milliampere

so

I = 0.04581 × 1000

I = 45.81 mA/cm²

Therefore, current density in milliamperes per square centimeter is 45.81 mA/cm²