Galvanized vs. Galvalume Steel: A Comparative Analysis

Industrial applications such as building, roofing, siding, and construction require top-tier materials for enhanced strength and protection against corrosion and various environmental conditions. When compared with standard steel, both galvanized and galvalume steel products offer greater wear protection and an assortment of potential applications. Within this blog we’ll explore the similarities and differences of galvalume and galvanized steel, including applications and benefits, providing the information you need to make an informed choice.

What is Galvanized Steel?

Galvanized steel is a carbon steel alloy that’s been coated with a sacrificial layer of metallic zinc that shields and protects the underlying steel substrate, providing enhanced corrosion resistance.

Galvanized Steel Manufacturing Process

The most common method of manufacturing galvanized steel is the hot-dipping method. Within this process the steel is submerged in a bath of molten zinc, which metallurgically bonds to the steel surface. Additional steps in the galvanized steel manufacturing process include:

Surface Preparation

Surface preparation is a vital step in the galvanization process since the steel surface must be spotless for the zinc to bond properly. Surface preparation steps include:

• Degreasing

• Pickling

• Rinsing

Flux Solution Application

To prevent flash rusting before galvanizing and to promote uniform zinc wetting, parts are dipped in a flux solution (typically zinc ammonium chloride). Flux also helps the steel enter the zinc bath without oxidation.

Hot-Dip Galvanizing

The hot-dip galvanization process includes the following steps to ensure a thorough application and proper bonding:

• Molten Zinc Bath - Steel is immersed in a kettle of molten zinc maintained at about 450 °C (840 °F).

• Metallurgical Bonding – Zinc and iron diffuse to form a series of zinc-iron alloy layers topped by nearly pure zinc. This metallurgical bond ensures the coating won’t peel off under regular service.

• Dwell Time & Withdrawal - Components remain in the bath just long enough for the coating to build to the specified thickness (commonly 45–70 µm).

Cooling & Passivation

To ensure continued proper bonding, the newly galvanized steel is cooled in standard air or via a freshwater spray that solidifies the zinc layer. Passivation techniques are also commonly utilized via a chromate or silicate dip that can enhance the coating’s corrosion performance and impart a uniform finish color.

Quality Control & Inspection Process

Quality control standards are imparted on the freshly galvanized steel through the following processes:

• Coating Thickness Measurement - Magnetic or electromagnetic gauges verify zinc thickness meets standards (e.g., ASTM A123 requires ≥ 45 µm for most applications).

• Adhesion & Appearance Check - Visual inspection ensures even coverage, minimal spangle (crystalline pattern), and absence of bare spots or excessive runs.

Galvanized Steel Applications

Typical applications for galvanized steel include:

• Structural Components

• Storage Tanks

• Irrigation Systems

• Plumbing

• Fencing

• HVAC

• Metal Siding

• Telecommunication Equipment

What is Galvalume Steel?

Galvalume is a steel that is hot-dipped in a molten bath of aluminum and zinc alloys that provides superior protection against rust and corrosion compared to galvanized steel. Galvalume is primarily used for roofing, siding, and various other industrial applications. Galvalume steel can last 60 years or more, making it a cost-effective solution versus other steel alloys.

Galvalume Steel Manufacturing Process

Galvalume steel combines the corrosion resistance of aluminum with the sacrificial protection of zinc in a single, alloyed coating. The most common method for producing Galvalume is hot-dip alloy coating. Galvalume manufacturing steps include:

Base Steel Preparation

A thin sheet of carbon steel is first produced by hot rolling, pickling, and then cold rolling to the final gauge. Surface cleaning is then conducted to remove grease and oil. After rinsing the steel, an acid-picked process eliminates mill scale and surface oxides.

Flux Bath

After the base steel is prepped, the clean steel is then passed through a zinc-ammonium chloride flux solution. This prevents oxidation and promotes uniform wetting in the subsequent molten bath.

Molten Bath Alloy Coating

The molten alloy bath is a two-step process and consists of approximately 55% aluminum, 43.4% zinc, and 1.6% silicon by weight. The two-step process includes the following steps:

• Immersion – The steel strip is passed through the 450–460 °C (840–860 °F) alloy bath on an entry roll.

• Metallurgical Bonding – During this process, aluminum rapidly forms a thin barrier layer on the steel’s surface while zinc and silicon diffuse at the interface, creating a graded alloy structure.

Cooling

During the cooling process, controlled pressure jets are blown onto the freshly coated strip to regulate coating thickness and create a uniform, smooth finish. The steel is then water-quenched or air-cooled to solidify the alloy.

Optional Post-Coating Treatments

The optional final stage is where passivation, oiling, or clear coating treatments are applied. Passivation consists of a chromate or silicate dip that may be used to enhance initial corrosion resistance and improve paint adhesion. Oiling and clear coating protect the fresh alloy from fingerprinting and handling damage.

Galvalume Steel Applications

Galvalume steel is commonly used in the following applications:

• Metal roofing and wall panels in coastal homes and commercial buildings

• Architectural facades where aesthetics and longevity matter

• HVAC equipment requiring long-term weather resistance

• Agricultural buildings prone to moisture exposure

Galvanized Steel vs. Galvalume Steel: Which is Right for Your Project?

Both galvanized and galvalume steel offer varying benefits and advantages, so there is no simple answer as to which product is better than the other. Basically, it all comes down to the application specifications, budget, and overall need. For example, galvanized steel performs very well in most inland and moderately corrosive environments. At the same time, galvalume excels in coastal areas with salt spray and regions with heavy UV exposure where barrier protection against moisture and sun is critical. The table below offers a side-by-side comparative analysis.

IMS is Your Locally Trusted Provider of Galvanized & Galvalume Steel

With seven locations serving California, Arizona, Nevada, and Northern Mexico, IMS is your trusted source for premium galvanized and galvalume steel products, including galvanized steel sheet and plate, galvanized square steel tube, and corrugated sheet metals and panels for roofing, siding, and other building applications.
 At IMS, we offer the following advantages:

• Same-day will-call pick-up

• Next-day local delivery

• Excellent high-volume discount pricing

• Advanced precision cutting services

• ISO 9001 certified

• Support of Just-In-Time manufacturing processes

• No minimum purchases

Purchase Galvanized & Galvalume Steel Products Today

Contact us for more information regarding our in-stock galvanized and galvalume steel products and secondary service options. Our experts will assist you in finding the steel product that meets your project specifications.