FAQ - STEEL

What is Hot-Dipped Galvanized?

Hot-Dipped Galvanized is normally a cold-rolled steel (depending on gauge, may be a hot-rolled base) which has been given a process by which a coating of zinc has been applied to the surface. This zinc has excellent adherence to the surface of the base steel.

Why put zinc on the surface of steel?

The purpose of the zinc is to provide excellent protection against corrosion of the base steel. The zinc is a sacrificial barrier to protect the base steel. The zinc will sacrifice itself and will eventually disappear before the base metal will start to corrode.

What qualities of Galvanized steel are available?

• Commercial Steel (CS)

• Forming Steel (FS)

• Structural Steel (SS)

• Deep Drawing Steel (DDS)

• Extra Deep Drawing Steel EDDS)

• High-Strength Low Alloy.

What is Commercial Steel (CS)?

This galvanized product can be subjected to simple bending or moderate drawing. It can be bent flat on itself in any direction at room temperature.

What is Forming Steel (FS)?

Compared to CS, this product has a greater degree of ductility and is more consistent in forming performance.

What is Deep Drawing Steel (DDS)?

Compared to FS, this product has more stringent drawing requirements and is normally suitable for deep-drawing applications.

What is Structural Steel (SS)?

This product is furnished when certain strength levels or mechanical properties are required. Usually these applications involve roll forming or brake press bending. Mechanical properties such as yield and tensile strength, and elongation in 2" can be reported and test reports issued, if requested.

What is Extra Deep Drawing Steel (EDDS)?

If EDDS is ordered, the purchaser can expect the mechanical properties of the galvanized not to change over time.  Aging will not be a factor with this product.  This product usually has superior drawing and stretching properties.

What is High-Strength Low Alloy (HSLA)?

This product has the high strength associated with Structural Steel but improved forming properties.

What is ASTM A653?

ASTM A653 is the broad (industry accepted) specification covering most of the "Qualities" of the galvanized products listed above.

What is Aging?

Aging is a phenomenon in which the atomic makeup of a non-stable steel undergoes changes over time with the result that the mechanical properties change over time. The yield and tensile strength increase, and the elongation decreases. There may be a return of the yield point which could cause stretcher strains to occur during forming of the steel.

What surface finish or types of coating can be ordered?

REGULAR SPANGLE - the normal finish of zinc crystal or "flower" on the surface of the galvanized steel.

MINIMIZED SPANGLE - the surface is altered soon after the product has been coated with the result that the zinc crystal formation has been suppressed. The surface normally is dull with very little spangle present. The product may not have a uniform surface across the width or from coil to coil.

FINE SPANGLE - the processing has been controlled to produce a much smaller and more uniform spangle than the regular spangle product. This is not available on all sizes.

EXTRA SMOOTH - the coil has been skin passed (temper rolled) to produce a surface which is smoother than the regular, as coated, product. This is often ordered when the surface is critical and/or will be painted. The zinc crystal is not visible.

GALVANNEALED (ALLOYED) - this product has its surface altered by heat treatment before the zinc has solidified after emerging from the galvanizing pot, and is entirely an iron-zinc alloy coating. The surface will be a dull gray and does not have a spangle. This product was developed for use in applications where the product will be painted (with suitable preparation) or welded. It must be noted that this coating does not have the ductility of the other finishes and may have a tendency to powder when subjected to severe forming.

What is chemical treatment?

This is a passivating treatment applied to the surface of galvanized steel to delay the onset of "white rust" or "wet storage stain." The user is cautioned that galvanized ordered with chemical treatment is not always compatible with products used when the galvanized is to be painted or have other surface treatments.

What is white rust or wet storage stain?

White rust is the initial, visible product of the oxidation of the surface of the galvanized. The product incurs white rust long before the product tarts to red rust.

What can be done to protect against white rust?

The product can be ordered with chemical treatment or oil on the surface to help protect the surface against staining when in contact with water. It is recommended the customer order chemical treatment or oil. The protection with chemical treatment or oil on the surface is generally believed to be better than both chem treat and oil together. In addition, the customer should not allow the galvanized product to be exposed to water or dampness for extended periods of time. Every precaution should be taken to prevent the product from getting and staying wet. If sheets do get wet, they should be stored in such a manner that they are allowed to dry. The galvanized product should be stored in a warm, dry environment. The paper wrapping should not be removed from the coil until the steel has reached room temperature, normally after 72 hours at room temperature.

Are galvanized products guaranteed for minimum results in a salt-spray test?

No, due to the inherent variances in the production of the product. In general, the more zinc on the surface, the greater number of hours can be expected prior to the formation of red rust in a salt spray test. (Laboratory test data is available upon request.) Additionally, although salt spray testing procedures are available as a specification, there are inconsistencies in the test apparatus so as to make the results non-reproducible.

How is the amount of zinc coating measured?

The amount of zinc is normally measured in ounces per square foot of surface. Specific testing procedures have been established to measure the amount of zinc. A less precise method is to measure the thickness of the zinc.

What are coating designations or coating weights?

Coating designations or coating weights are the terms used to describe the amount of zinc as the total coating on both surfaces.

What are "G" coatings and what are "A" coatings?

Regular galvanized is ordered with the designation of "G" coatings. Alloyed coatings are ordered with the designation of "A" coatings. Normal designations for the regular zinc galvanized product are G90 and Three test pieces (edge-center-edge), taken in accordance with ASTM standards, are stripped of coating by an approved method, and the coating is determined by the average difference in weight before and after stripping.

What is the single-spot test?

One test piece, from any part of a sheet, is stripped of coating by an approved method, and the difference in weights of the single piece determines the coating weight.

What gauge tolerance can be expected with galvanized products?

We guarantee 1/2 gauge tolerance to 0.075" thickness and 3/4 gauge tolerance to thickness greater than 0.075".

How much bending or forming can the zinc coating withstand?

The zinc coating shall withstand bending, without flaking (peeling), when tested in accordance with provisions in ASTM A653. There are no established standards with respect to flaking of the coating during drawing operations; hence, this is subject to negotiation.