Will galvanizing cause rust? What is the difference between galvanized steel and stainless steel?

In our daily life, we see rusted pipes, chains, tarnished silver jewelry, steel structural components, and car bodies. Why does this happen?

According to thermodynamics, every metal and alloy tries to obtain the lowest possible energy. Unsaturation of metals with water, metal, air, or other factors may lead to corrosion. During the corrosion process, metals and alloys try to reach the lowest possible energy state by chemically reacting with the surrounding environment. It not only degrades the mechanical properties of the component, but can also lead to catastrophic failure of the component. Therefore, corrosion of metals and alloys has emerged as a whole field because it has a direct impact on the economy. Since the corrosion costs are huge, it is difficult to estimate.

According to data from renowned organizations, the losses amount to 3-4% of the gross domestic product (GDP), which in the case of the United States is around hundreds of billions of dollars. India’s losses are around 5% of its GDP every year. Corrosion cannot be ruled out or reduced to zero as repairs and replacements of components require huge financial support. There are methods or techniques to reduce it, which include protective coatings in the form of metal plating, protective coatings and sacrificial coatings, and some other parameters.

The difference between galvanized and stainless steel

Since both galvanized steel and stainless steel have been discussed in detail separately. In order to better understand the subject and make better use of these two steels, a comparison is required. The differences between stainless steel and galvanized steel will be discussed below.

Corrosion Resistance

When comparing the corrosion resistance of the two steels, steel has excellent corrosion resistance, while galvanized steel has low to moderate corrosion resistance. Galvanized steel can be used in less corrosive environments, but is not suitable for highly corrosive environments, such as marine and acidic environments. Instead, stainless steel is recommended for marine environments. Over time, the zinc coating will wear away, which is not the case with stainless steel.

Is galvanized steel strong?

Galvanized steel is strong, but its strength depends on the carbon steel underneath. The zinc coating on the surface of the substrate provides corrosion protection by forming a sacrificial cell on the carbon steel. The protective layer formed by the chromium in stainless steel is very thin, but stainless steel still provides good strength. Due to its chemical composition and microstructure, stainless steel has a higher strength range than galvanized steel.

Appearance and aesthetics

Stainless steel has a gleaming, bright metallic appearance, the brightness of which varies with the grade. It has a textured, glossy, matte and brushed appearance, depending on the requirement. Galvanized steel has a dull grey or silver grey appearance with a textured surface. Over time, the appearance of galvanized steel will take on a weathered look, becoming more uniform in color as it ages, without compromising uniform corrosion resistance.

Fire resistance and welding considerations

Due to welding considerations, galvanized steel is difficult to weld compared to stainless steel. The zinc layer needs to be removed before welding because zinc produces noxious fumes that are harmful to health. Both types of steel have good fire resistance properties but will eventually lose strength and structural integrity when exposed to high temperatures for long periods of time.

Price and Application

The prices of both alloys depend on various factors, such as grade and processing technology. Generally speaking, stainless steel is more expensive than galvanized steel. Galvanized steel is used in information structures, construction, agriculture, automobiles, and electronics, while stainless steel is used in medical, hospitals, food containers, automobiles, and the aerospace industry.

Summary of differences

	Galvanized Steel	Stainless steel
Corrosion resistance	Low to medium	high
Durability	Relatively low	Relatively high
longevity	Relatively low	Relatively high
strength	Low strength carbon steel	High-strength stainless steel
Porous	have	NO
application	Infrastructure, construction, galvanized pipes, galvanized steel sheets	Medical and food containers