The present invention provides for a method of decreasing the Conradson carbon content of metal containing petroleum streams by forming a mixture of the Conradson carbon containing petroleum fraction and an aqueous electrolysis medium containing an electron transfer agent, and passing an electric current through the mixture or optionally through the pretreated aqueous electrolysis medium at a voltage, sufficient to decrease the Concarbon content of the stream. The cathodic voltage is from 0 V to -3.0 V vs. SCE. The invention provides a method for enhancing the value of petroleum feeds that traditionally have limited use in refineries.