Methods and compositions for preventing precipitation of iron compounds during acid treatments of wells by catalyzing the rate of iron reduction during such treatments. Reduction of ferric ions is accelerated utilizing co-catalytic amounts of antimony ions in combination with other materials to minimize precipitation and other complications which result from iron compounds during acid treatments. Such other materials may include co-catalytic amounts of copper ions and optional iodide ions; as well as at least one of phosphinic acid, salt of phosphinic acid, or a mixture thereof.