No, they used to be made from copper or brass.
Radiators are made of a lot of metals with high melting points (example: Aluminum)
Aluminum
aluminum and copper
100 for old one and 200 for aluminum
most car radiators are copper or aluminum and plastic.
Aluminum radiator equipment is more efficient for cooling, it is also cheaper and lighter than copper and brass types. Aluminum is easily recycled, whereas brass radiators are more difficult due to the solder used. Aluminum may corrode a little faster than other types, but many coolants are being made now that are more compatible with aluminum radiators. Aluminum is also a bit more difficult to repair than other types of metals that are used in radiators.
Almost all car manufacturers have used cast iron radiators at one time or another, however most are now made of an aluminum alloy that can cool the water intake quickly.
Older vehicles had copper and steel radiators, newer vehicles are made of aluminum and plastic.
Mostly lawn mowers and tractors trailors are the two most important parts that need alumium radiators. They are pretty expensive if one of these parts breaks.
Yes, it can be welded, depending on the location of the crack. Some radiators are repairablbe, depending on the construction of the radiator. Older style all-brass/copper radiators can be soldered (not welded) if the leak area is accessible and the surrounding metal is strong enough. Some newer style plastic tank/aluminum core radiators can be repaired if the leak is at the joint between the tank(s) and the core, while others cannot. The plastic tanks themselves and the aluminum cores cannot be reliably repaired.
Most car radiators are made of aluminum or a combination of aluminum and plastic, which are not susceptible to rusting like iron or steel. Additionally, the cooling system in cars is filled with coolant that contains corrosion inhibitors to protect the radiator and other components from rusting. Regular maintenance, such as flushing and replacing the coolant, also helps prevent rusting.
Aluminum radiators are lighter and cool almost as good as a copper/brass unit does. If they are both new then copper is going to cool better ,but the aluminum is up to 60% lighter.