Pure iron, pig iron reacts with dilute acid that fast? Why?

Pure iron, pig iron reacts with dilute acid that fast? Why?

Pure iron and dilute sulphuric acid need heating. The pig iron is not, it contains other metal impurities, can form galvanic battery reaction

Pig iron is quick. Carbon, iron, dilute sulfuric acid in a pig iron form a battery

Compared with the hydrochloric acid of the same concentration, the rate of iron formation in the pig iron is faster than that of pure iron, because the parallel reaction of the galvanic cell occurs in addition to the normal substitution reaction of the pig iron