When iron, Fe is in contact with a solution of pH 9 and above, it does NOT rust. Why?

Question

My chemistry textbook just throws this question at me without any answer available. Help please.

Answer 1

You haven't gotten any takers on this question in over an hour, so I shall throw in my 2-cents.

Rust is often thought to be Fe2O3, but in humid environments, rust exists as FeO(OH) and even Fe(OH)3 in water.

But in very basic solutions the solid Fe(OH)3 is soluble as Fe(OH)4-.  This is why solutions of sodium hydroxide can be used as rust remover.

So even if the iron oxidizes in the present of oxygen and water, there will be no deposit of solid rust.