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An autodeposition bath for coating steel and similar metals is operated initially with a low content of dissolved iron and at a high oxidizing potential. After the iron content has increased beyond a specific level, such as 1.5 g/l, the oxidizing potential is reduced. This permits continued satisfac

An autodeposition bath for coating steel and similar metals is operated initially with a low content of dissolved iron and at a high oxidizing potential. After the iron content has increased beyond a specific level, such as 1.5 g/l, the oxidizing potential is reduced. This permits continued satisfactory operation of the bath with lower rates of iron accumulation in the bath, so that the need for bath stabilization by removing dissolved iron is deferred.

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A method of operating an autodeposition bath, comprising the steps of: (a) providing a bath comprising (i) stable, autodepositable polymer, (ii) acid in sufficient quantity to maintain the pH of the bath at not more than about 4, (iii) a soluble oxidant in sufficient quantity to maintain the redox p

A method of operating an autodeposition bath, comprising the steps of: (a) providing a bath comprising (i) stable, autodepositable polymer, (ii) acid in sufficient quantity to maintain the pH of the bath at not more than about 4, (iii) a soluble oxidant in sufficient quantity to maintain the redox potential of the bath at least about 425 mv more oxidizing than a silver-saturated silver chloride electrode, and (iv) a concentration of soluble iron less than a specific value; (b) contacting the bath provided in step (a) with ferriferous active metal surface, so as to cause autodeposition of polymer thereon and to cause the concentration of soluble iron in the bath to increase, while simultaneously maintaining the redox potential of the bath at least about 425 mv more oxidizing than a silver-saturated silver chloride electrode by supplying additional soluble oxidant to the bath as needed, until the concentration of soluble iron in the bath exceeds said specific value; and (c) contacting the bath, after completion of step (b), with additional amounts of ferriferous active metal surface, so as to cause autodeposition of polymer on the active metal surface from the bath while simultaneously maintaining the redox potential of the bath at a value not less than about 272 mv and not more than about 375 mv more oxidizing than a silver-saturated silver chloride electrode by supplying additional soluble oxidant to the bath as needed, wherein the average rate of increase of soluble iron in the bath, per unit area of active metal coated, during step (c) of the process is less than during step (b).