DO NOT COOK WITH GALVANIZED METAL. You cant cover the galvanized with soot, if you got it really hot all you did was expose more harmful elements.
http://zenstoves.net/Warning.htm
Galvanized Steel
Galvanized steel should never be used for cookware or food storage since this may lead to zinc poisoning (aka heavy metal poisoning). Exposure to high levels of zinc can cause lethargy, dizziness, nausea, fever, diarrhea, irritability, muscular stiffness and pain, loss of appetite, and reversible pancreatic and neurological damage.
Pot stands and stoves constructed from galvanized steel can cause metal fume fever when heated. This is caused by the inhalation of zinc oxide fumes or dust produced when galvanized steel is welded or burned. The signs and symptoms can be vague (shaking chills, fever, body aches, headache, and fatigue) and are similar to those of the flu or a viral illness. Onset of symptoms often occur after well after exposure (3-10 hours) and makes the connection between using your stove and sickness less obvious than one would think. Symptoms usually resolve after 48 hours if you quit cooking with galvanized steel.
Metal Fume Fever has been linked with occupational asthma and is a pretty noxious illness.