Galvanized Steel and How It Works (2023)
Will Galvanized Steel Rust?
Galvanized steel is steel that has been molten with a layer of zinc to protect it from corrosion. While it is more resistant to rust than untreated steel, it is not completely immune to rusting. Over time, the zinc layer can corrode and wear away, especially in harsh environments or if the zinc layer is totally compromised. Under normal usage and conditions, this may take at least 10 years before it happens. When maintained properly, Galvanized Steel Boltless Racks are capable of staying rust-free after 10 to 20 years of usage. Here are some TLDR notes:
- Galvanized Steel is the cheaper alternative to Stainless Steel. It protects via sacrificial protection and doesn't require a layer of coating to resist rust.
- You can use surface cleaner and damp cloth to clean it. It is recommended to spray the cleaner on a cloth then wipe.
- Do not let liquids puddle on the surface for prolonged period of time (i.e. a box with liquid chemical content leaking at the base). This will accelerate the rust process.
- Do not let strong chemical puddle on the surface for prolonged period of time (i.e. a bleach bottle with its base still wet with bleach). Most if not all metals will corrode when they come in contact with strong chemical, often in matter of days or weeks.
Galvanized steel is commonly used in applications where corrosion protection is needed without the cost of stainless steel and can be identified by the crystallized pattern on the surface (often called a ‘spangle’). If you look around, you will realize that Singapore's street lamp posts, highway barriers, street fences, drain covers and sheltered walkways are made of Galvanized Steel.
What is Hot-dip Galvanizing?
Hot dip galvanizing is the process of protecting iron or steel with a layer of zinc by immersing the metal in a bath of molten zinc at a temperature of around 450 °C (842 °F). During the process, a metallurgically bonded coating is formed which protects the steel from harsh environments, whether they be external or internal. It is considered to be the most environmentally friendly process available to prevent corrosion.
Difference between Galvanizing and Powder Coating
A primary difference between galvanization and powder coating is the way they protect the surface of the work-piece.
Galvanizing provides a barrier protection between all internal and external steel surfaces and their environment. Unlike a paint coating, the metallurgical bond that is formed through galvanizing becomes part of the steel itself and is not merely a chemical or mechanical bond. Zinc corrodes in preference to steel and sacrifices itself to protect the steel, hence hot dip galvanizing will provide this sacrificial protection. The corrosion residue from the zinc (zinc oxide) are deposited back on the steel resealing it from the atmosphere and therefore stopping corrosion. This is why white substances may form on galvanized steel over time.
Powder coating works by forming a protective barrier that prevents destructive materials from penetrating and reaching the surface. However, powder coating is porous and can easily damage under force or hard scratches. Once penetrated, the corrosion resistance is compromised and moisture can reach the underlying layer of metal easily. This is why users often find their metal racks corroding and rusting beneath the layer of powder-coat, that is supposed to protect it.
With galvanized steel as the underlying material, even with no powder-coat or if the powder-coat is scratched, it will not rust easily and spread internally beneath the layer of powder-coat.
Benefits of Galvanized Steel
- Less Maintenance Required – Self-maintaining and thicker, resulting in lower maintenance cost of steel items.
- Longer Life – Under normal atmospheric condition, it can last in excess of 10 - 20 years, continually protecting steel against corrosive elements.
- Lower Costs – Lower initial cost than a lot of other commonly specified corrosion protection coatings for steel, such as Stainless Steel and Chrome Plating.
- Environmentally Friendly – The longevity of the maintenance-free coating provides environmental and economic benefits. Zinc exists naturally in the world so the zinc byproducts released into the atmosphere are not harmful.
Using Galvanization and Powder Coating Together
It’s possible to combine hot-dip galvanizing with powder coating to form a duplex system for protecting metal materials. The galvanized steel serves as a base finish that enhances corrosion protection. The powder coating provides a top layer that slows down the rate in which corrosion consumes the underlying zinc. The powder coating can also improve the aesthetic appeal of the metal object.