Most headers are made of two materials, mild steel or stainless steel. Mild steel is sort of the “entry level” point for headers. Mild steel headers are typically much cheaper to purchase; however, they are far more prone to oxidation and rust. Stainless steel headers will cost a significant amount more at the initial purchase, however, they will typically last much longer. Stainless steel will not rust and is better at retaining heat. This results in lower under-hood temperatures, and cooler air making its way inside the engine.
Once you decide upon the construction material, you also will have to choose an exterior finish for your header(s). There are 3 basic finishes: bare, painted, and ceramic coated.
Bare headers: are exactly what they sound like, no finish on the header. These are typically priced the lowest, but have the shortest length of service. As you can imagine, a piece of steel without any protection, being subjected to water, road salt, and engine compartment temperatures, will eventually corrode.
Painted headers: are basically the “middle of the road.” They are slightly more expensive than bare headers and will last slightly longer. These headers are coated with a high-temperature paint. It provides a basic layer of protection, but as it ages and begins to chip, corrosion will eventually become a problem.
Ceramic coatings: are the “top of the line” in the header game. Ceramic coatings protect the appearance and integrity of the header, as well as keep heat inside the header tubes. This prevents corrosion, and keeps under-hood temperatures lower, allowing a cooler, more dense charge of air to reach your engine. This means more horsepower.