Corrosion at breaker connections

I did an inspection today and found corrosion at a double breaker for the clothes dryer–40 amp. The corrosion is at the 3rd terminal form the top in the attached photo. A portion of the cable sheathing appears to have melted. I ran the dryer for 20 minutes and neither the terminal nor the cable overheated. Can anyone give me a reason for the corrosion and the previous overheating?

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May be from previously loose connection at the terminal on te breaker that may have caused an arcing condition that melted the sheathing - Ask the current owner if any recent repair has been conducted to the dryer or branch circuit -some wire/cables can loosen from expansion & contraction or not enough torque on the terminal to fasten cable in place

Regardless, it needs a repair by a qualified electrician.

John Kogel

Thanks for your replies and I did recommend that an electrician inspect, clean and repair the deficiency.

Did you note that the breaker was incorrecly sized for its purpose? In 30 years I have never seen a residential dryer that required more than 30 amps at 240 volts.

Also shouldn’t the white wire next to it be marked with electrical tape as hot?

What guage is that burnt wire. Looks small.