What is Galvanized Steel?
Galvanized steel is coated with a thin layer of zinc. The zinc coating protects the steel beneath it from rust. It’s used to make nuts, bolts, screws, and nails resistant to degradation when they are exposed to the weather. Galvanized steel stands up to water well — as long as it’s not salt water. Welders who work with structural steel can work with galvanized steel, although they will need protection against breathing the fumes.

What is Stainless Steel?
Stainless steel is made by adding chromium to molten steel. It is unusually strong and resistant to rusting caused by contact with water, even salt water. Welding stainless steel is a specialized skill. Welders must exercise much more control when heating and cooling stainless steel. And they must take special care to match filler materials with the steel being welded.

Engineers and architects need to keep up with differences in types of stainless steel. Austenitic stainless steel is the product you might use in a machine shop. Ferritic stainless steel is a cheaper product that is used in applications that are easy to replace, like automobile exhaust pipes. Long-wearing martenistic steel is used for hardfacing. Duplex stainless steel combines the molecular structures of austenitic and ferritic stainless steel but it is hard to work with. Precipitation-hardening stainless steel is made by adding another rare metal like niobium for even more strength, most often for aerospace applications. The more complex the alloy, generally the greater the strength, the higher the price, and the greater the labor costs.

In general, galvanized steel is more ductile, and easier to work than stainless steel. Stainless steel is stronger and more corrosion-resistant than galvanized steel.

What is the Difference in Price?
Galvanized steel is almost the same price as untreated structural steel. Stainless steel costs four to five times as much as galvanized steel and untreated structural steel. Niobium alloys are even more expensive.

Which Kind of Steel Stands up Better?
As you look through the characteristics of these two types of steel, you can see they are very different from each other. Both kinds of steel are applicable to a huge range of products, but one type will always be a better choice than the other.

There are situations in which you need to stay away from stainless steel. This product stands up to salt water, but it is quickly degraded after exposure to chlorinated water. You also need to avoid any design in which two stainless steel components generate friction against each other. They can weld themselves together.

As great as galvanized steel is, there are also situations in which the choice of galvanized steel needs additional consideration. Usually, steel should be welded before it is galvanized, not after. Welding steel after it has been galvanized burns away the protective layer of zinc at the weld. It may be necessary to regalvanize galvanized steel after it is welded to protect the joint.

If you are building the rocket that will send the Space Force to Mars, you will probably need to work with stainless steel. You will also need stainless steel if you get a contract to build an ocean-bound submarine. But for most down to earth uses of steel on land, your most economical choice, in terms of both material and labor costs and life of the project, will be galvanized steel.