Question

How does the tendency of iron to rust depend on ph?

Answer 1

The  tendency  of  iron  to  rust   depend  on  the  Ph   of solution

 The   formation  of  rust  increases  as  the  PH  decreases.  This  led  agent  of  rusting  that  is  oxygen  gets  more  positive  as  H+  ions  increase   which  facilitate     rusting. The    lower  the  Ph  level  the   quick  the   corrosion.

Answer 2

Rust occurs when an area of  an iron or a ferrous allow such as steel drops below a pH of about 8.2 or 8.3. 
Formation of rust increases as the pH decreases.
Rust is chemically known as hydrated iron (iii) oxide, oxygen gets more positive as H+ increases.