Fastener Materials 101 | Stainless Steel Versus Galvanized Steel
Despite the fact that both alloys include the same basic metal, stainless steel and galvanized steel are actually very different materials that are suitable for various applications. Galvanized steel is essentially steel that has been coated with zinc to increase its corrosion resistance. Stainless steel, on the other hand, is an alloy that includes steel and at least 10% chromium, which is added in the molten metal mixture. Let's explore the main distinctions between these common fastener materials.
As previously mentioned, stainless steel is obtained by adding chromium while the metal is in a liquid state. Take note that stainless steel must include at least 10.5% chromium in addition to the regular carbon steel alloy, as otherwise, it can't be classified as stainless. After the alloy cools down, it can be subjected to pickling to remove all impurities from the surface and passivation, a process that adds a non-corrosive layer on the surface.
Galvanized steel is obtained by applying a small coat of zinc over the metal to enhance its anti-corrosive properties. The zinc can be applied by hot-dipping, a process that implies submerging the steel into a hot bath of liquid zinc. Alternatively, the same results can be obtained via electrogalvanization, which is accomplished by submerging the steel in an electrolyte bath.
Even though the materials are obtained with different processes, in the end they serve the same function: both protect the core metal from corrosion by creating a controlled layer of protective oxide. While the stainless steel’s sacrificial layer is almost invisible, the one formed due to galvanization is considerably thicker.
Lifespan and durability
Because the zinc in stainless steel has been fused with the metal while it was still in its liquid state, it means that the protective layer will be replenished. Due to the same reasons, stainless steel will not rust, regardless of the severity of the dents or scratches it suffers.
On the other hand, galvanization's thin oxide layer will wear away in time, leaving the steel vulnerable to corrosion. Because the coating has less than one millimeter in thickness, even the smallest scratch could lead to localized rust in certain circumstances.
A quick look over the price of galvanized and stainless steel bolts will reveal that the latter are more expensive; material costs wise, the price of stainless steel is four to five times higher than its galvanized counterpart. In addition, let's not forget that the price of steel changes every day, based on supply and demand as well as the energy prices. Consequentially, using galvanized steel bolts in applications that rely on thick metallic components, such as machine housing or buildings, will drastically decrease the overall costs.
Galvanized steel fasteners are best used in home construction projects or for ornamental fencing. In fact, most outdoor ornamental fences you think are made of iron are in fact constructed from galvanized steel. The material is also commonly employed in household appliances that may be exposed to water as well as heavy-duty frames for buses and trucks. Given its strength and resistance to rust, stainless steel is often preferred in constructions, pipeline manufacturing and marine environments, but also in cutlery.
About the Author
Started my career in the fastener world in 1969 at, Parker Kalon Corp. a NJ based screw manufacturer located in Clifton, NJ working in inventory control, scheduling secondary production and concluding there in purchasing. In 1971 I accepted a sales position at Star Stainless Screw Co., Totowa, NJ working in inside sales and later as an outside salesman, having a successful career at Star I had the desire with a friend to start our own fastener distribution company in 1980 named: Divspec, Kenilworth, NJ. This was a successful adventure but ended in 1985 with me starting Melfast in August 1985 and have stayed competitive and successful to date. Melfast serves the OEM market with approximately 400 accounts nationally.