Electrogalvanized Steel VS Hot Dipped Galvanized Steel

What is Galvanized Steel?

Galvanized steel is coated with zinc to help prevent corrosion. Zinc forms a barrier, defending the metal itself from rust and other forms of corrosion. In addition, zinc reacts with oxygen when exposed to the atmosphere, thus forming zinc oxide. Furthermore, the zinc oxide reacts with carbon dioxide to firm a zinc carbonate. This stops further corrosion in most circumstances, safeguarding the steel from the element, particularly in areas with extreme exposure to saltwater. 

Alliance Steel sells and processes Hot dipped galvanized steel and Electrogalvanized steel. Our processing capabilities for galvanized steel sheet and coil services include slitting, shearing, blanking, stretcher leveling, and metallurgical support.        

What is the Galvanizing Process?

What is the Hot Dipped Galvanized Steel Sheet and Coil Process?

There are three main steps to making hot-dipped galvanized steel: surface preparation, galvanizing and post-treatment. 

Surface Preparation: For the zinc to react, the steel must be cleaned of all contaminants and oxides. First, the steel needs to be degreased. This degreasing bath removes contaminants such as oil, dirt, and/or grease from the surface of the steel using an alkaline solution and then rinsed with water. The next step is pickling. Next, the steel is submerged in a bath of hydrochloric or sulfuric acid. This bath removes the scale and oxides and once again rinsed with water. The last step in the surface preparation is fluxing. Fluxing removes all oxidation created during the pickling process and creates a protective coating on the steel before the galvanization. 

Galvanizing: Once the steel had been completely cleaned, it's ready for its hot-dipped bath in zinc. The process starts with submerging the carbon steel (hot roll or cold roll substrate) into a hot bath (680 degrees F) of zinc. As the steel cools, an iron- zinc alloy bond occurs, creating a spangled finish.

Post–Treatment: In some cases, the newly galvanized steel may go through further processing. The most common post-treatment for galvanized steel is quenching. This process helps protect the steel in transportation and storage. 

There is an increasing demand for hot-dipped galvanized products. This is due to higher market demand in transportation, telecommunications, and high voltage transmissions.

What is the Electrogalvanized Steel Sheet and Coil Process?

The zinc coating is applied to the steel by the process of electrodeposition. This process can apply a protective coating to both sides of the steel with exceptionally uniform thickness.

Are you ready for a small science lesson? 

According to AZO MATERIALS, "In the electrogalvanizing process, a zinc layer is applied using an electric current. A zinc electrolyte bath equipped with two electrodes is utilized - an anode (positive pole) and the steel parts to be galvanized as a cathode (negative pole), to which current is applied.

Dissolved zinc is also included in the bath and is introduced as a concentrate through metering pumps, and a conducting salt, typically caustic soda (sodium hydroxide/NaOH), is also added to boost conductivity. Under the influence of the electric current, the zinc that is dissolved in the bath (Zn2+) is reduced on the cathode and then gradually deposited on the steel component surface (Figure 1)." 

Figure 1. Electrogalvanizing in an alkaline zinc bath

Source: Monitoring an Electrogalvanizing Process (azom.com)

What are the Benefits of Galvanized Steel?

Coated Steel has many benefits, from cost to environmental impact. Here are four reasons you should consider coated steel products and coils from Alliance Steel. 

Corrosion Resistance: The most beneficial trait of coated steel is its effectiveness in protecting against oxidation. 

Increased Product Reliability: Because of its durability and resistance to corrosion and abrasion, coated steel and coated steel products require less maintenance.

Efficiency: Zinc Coatings protect the base metal from corrosion and sacrifice themselves to save the underlying material. 

Lower Initial Cost: Coated steel, like hot-dipped, galvanized, and electrogalvanized, may have a lower initial cost, contact your sales rep for more information.

What Industries use Galvanized Steel?

Agriculture: Whether it's a farm tank for livestock, grain drying hoppers, or tractor parts, agriculture equipment is often exposed to the elements. Making coated steel ideal for the agriculture industry.

Automotive: Coated Steel's ability to ward off corrosion and its surface quality creates a partnership in the automotive industry. Electrogalvanized steel is often found in automotive car doors, hoods, and fenders.

Infrastructure: According to American Coatings Association, "Unprotected steel structures in harsh environments can lose as much as 1 mm in thickness in as little as five years. This loss contributes to structural weakness, and the steel must be replaced. A thin protective coating applied to the steel can slow or delay the corrosion process and significantly extend the life of the steel by 15 or more years, even in offshore environments." (Source: Infrastructure - American Coatings Association (paint.org))

Construction: Steel Framing is a prime example of coated steel products. Its mold and termite resistant. Steel structures don't warp and split like their wood counterpart while simultaneously providing long-term performance.