Gas tanks have become a subject of interest recently because of how much it costs to fill our tanks. As our Corvette's go-juice becomes more precious, it's appropriate to examine the hardware that holds and protects the gasoline. The tank itself is mostly hidden from view and keeps a fairly low profile in the maintenance category. Primary reasons for replacing a Corvette gas tank are rust damage (from inside or out), collision damage, and cosmetics (as in restoration).
The appearance of rust damage on or in gas tanks is a puzzler to some people. The tank was unpainted from the factory, but the silver-colored sheen of its surface looks somewhat similar to galvanized or galvanic plating. And the surface acts like it has some form of rust-preventative coating-entire areas can be rust-free, even though adjacent areas suffer from extensive corrosion.
The name of the coated steel used for gas tanks is Terne steel. This type of steel was primarily selected because of how the upper and lower halves of gas tanks are made. Each half is pressed from a flat sheet of Terne-coated steel. More specifically, each half is deep-drawn and the lubricity of the coating helps the steel slide on the tooling as the steep sides are formed. Terne steel has a dull gray finish from its coating, which consists primarily of lead with a little tin. Another attribute of this particular coating is it provides good corrosion protection when in contact with petroleum fuels.
Original Corvette tanks were made of Terne steel and had no zinc (galvanize) or nickel coatings according to Gary Whiting, president, Quanta Products LLC. The Quanta reproduction tanks are made with Ni-Terne steel, which has an additional flash coating of nickel applied to the steel before the traditional Terne steel lead-tin coating is applied on top. The underlying nickel coating provides a greater measure of corrosion protection.
We cover what's involved in removing and replacing a C2 or C3 gas tank and its related components.
For those readers who don't need to replace their tanks, there's a sidebar above on how to easily vacuum water and debris from the inside of the tank. This prevents corrosion or rust-through from the inside and helps keep down-stream parts, such as the carburetor and engine, clean and happy.
Tank Maintenance-Vacuum Water and Debris
Inevitably water and dirt get into a gas tank. Dirt that passes the fuel strainer can cause problems with everything downstream, from the fuel pump valves to the carburetor, and, ultimately, cause engine problems. The effect of water on these parts can be just as bad or worse. water is heavier than gas and settles into the lowest part of the reinforcing channels stamped into the tank, which can cause the tank to rust-through from the inside. Fortunately, it's fairly easy to remove any water and dirt from a gas tank of a '63 to '74 Corvette by using a length of hose and a small metal tube.