The rusting of steel may be promoted by brushing with HCl followed by brushing with hydrogen peroxide solution. What is the chemistry involved?
I understand the point of your question, here is a discussion of the associated science.
The process remains a classic electrochemical process where here H2O2 is a replacement for oxygen and the require $\ce{H+}$ is provided by the $\ce{HCl}$ which is also a source of chloride ions noted to promote corrosion as well as forming salts which are excellent electrolytes.
Some references, starting with a good depiction of the underlying electrochemistry, to quote:

Iron (or steel) rusting is an example of corrosion -- an electrochemical process involving an anode (a piece of metal that readily gives up electrons), an electrolyte (a liquid that helps electrons move) and a cathode (a piece of metal that readily accepts electrons). When a piece of metal corrodes, the electrolyte helps provide oxygen to the anode. As oxygen combines with the metal, electrons are liberated. When they flow through the electrolyte to the cathode, the metal of the anode disappears, swept away by the electrical flow or converted into metal cations in a form such as rust.

And some comments from ScienceDirect on the referenced chloride properties:

The chloride ions present in the water promote local corrosion such as crevice corrosion and pitting, and the higher the chloride content, the more corrosive the water.

I hope this helps.