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Steel deck finishes |
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 | ::Christian Audet, Eng.
Engineer, Cold-Formed Products
Canam Canada
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Iron, the principal element of structural steel, rusts when it comes in contact with oxygen and humidity. Since steel deck is a relatively thin material, it must be protected by a finish that is suited to its utilization. This article describes the range of finishes available at Canam and provides guidance in selecting the finishes used in the construction of steel buildings.
Canam maintains an extensive inventory of galvanized steel coils and a limited quantity of painted steel coils in the most requested colours. Our cold-formed products may also be coated with other types of protective finishes, depending on the volume ordered and the supplier's rolling schedule.
Definitions
::Galvanized Steel
Galvanized steel is basically steel covered in zinc. In Canada, Canam produces deck with two types of galvanized finishes: Z275 (G90), which offers pure zinc protection at the surface, and ZF75, which is a thinner zinc-iron alloy offering light zinc protection. The section entitled “Nomenclature of finishes offered by Canam” provides commonly used expressions for these two types of finishes.
::Painted Steel
The painted steel used by Canam consists of “black” steel coils pre-coated with a polyester-based paint. Painted steel may be used for deck that is exposed inside a building but it offers less protection against corrosion than Z275 galvanized steel.
::Prepainted 8000+ Series
The prepainted 8000+ Series consists of Z275 galvanized coils that have a polyester and silicone resin coating guaranteed to increase durability and resist corrosion. This Series can be exposed to adverse weather conditions.
::Zinc-Aluminum (AZM150)
The zinc-aluminum alloy finish over the base steel provides superior cathodic protection against corrosion.
::GalvalumeTM and Galvalume PlusTM
Galvalume is the Dofasco trademark for its zinc-aluminum finish (AZM150). Galvalume Plus has a resin finish applied to both sides of the sheet steel over the zinc-aluminum alloy finish.
::Barrier Series
The Barrier Series has a Z275 galvanized steel substrate with a factory-applied primer and a polyvinyl chloride (PVC) finish that can protect the steel in moderately corrosive environments.
::Stainless Steel
Stainless steel, which has a very resistant finish, has different physical characteristics from those of conventional structural sheet steel. Cost and availability are important factors to consider when stainless steel is specified.
Nomenclature of Finishes Offered by Canam
| Commonly used expressions | ASTM nomenclature of steel | Correct expressions to use | Notes |
SI | Imperial | SI | Imperial | |
| Galvanized | ASTM A 653M Z275 | ASTM A 653 G90 | Galvanized finish Z275 | Galvanized finish G90 | |
Galvanneal
Light zinc coat
Wiped zinc coat
Satin coat | ASTM A 653M ZF75 | ASTM A 653 A25 | Galvanized finish ZF75 | Galvanized finish A25 | 1 |
| Painted | ASTM A 1008M
+ paint | ASTM A 1008
+ paint | Polyester-based paint specifying colour code | 2,3 |
Prepainted
8000+ Series | ASTM A 653M Z275 + paint | ASTM A 653 G90
+ paint | Prepainted 8000+ Series specifying colour code | 2,4 |
Zincalum
Zinc-aluminum | ASTM A 792M AZM150 | ASTM A 792 AZ50 | Steel A 792M AZM 150 | Steel A 792 AZ50 | 2 |
GalvalumeTM
Galvalume PlusTM | ASTM A 792M AZM150 | ASTM A 792 AZ50 | GalvalumeTM
Galvalume PlusTM | 2, 4, 5 |
Barrier Finish
Barrier Series | ASTM A 755M
ASTM A 653M Z275 | ASTM A 755
ASTM A 653 G90 | Barrier Series specifying colour code | 2, 4 |
| Stainless steel | ASTM A 240M | ASTM A 240 | Stainless steel | 2 |
Note 1: ASTM A 653M ZF75 finish must be field-painted prior to occupancy of the building. Measures must be taken to protect the steel deck upon delivery.
Note 2: Not all steel finishes are kept in stock; minimum volumes must be ordered and delivery dates must be approved. Contact a Canam sales representative for more information on delivery dates as well as available thicknesses and colours for specific finishes.
Note 3: Usual colors are white and grey.
Note 4: Architectural finish designed to withstand adverse weather conditions.
Note 5: Dofasco trademark.
Coating Quantity
Minimum coating requirements are based on coating weight per unit of surface. The following table summarizes the principal coatings available for Canam steel deck.
Coating Weight |
Coating | Coating Designation | Minimum Coating Requirements |
SI | Imperial | Total Both
Sides in g/m² | Total Both
Sides in oz./sq. ft. |
Zinc-aluminum alloy | ASTM A 792M AZM150 | ASTM A 792 AZ50 | 150 | 0.50 |
ASTM A 792M AZM165 | ASTM A 792 AZ55 | 165 | 0.55 |
ASTM A 792M AZM180 | ASTM A 792 AZ60 | 180 | 0.60 |
Zinc-iron alloy | ASTM A 653M ZF75 | ASTM A 653M A25 | 75 | 0.25 |
Zinc | ASTM A 653M Z180 | ASTM A 653 G60 | 180 | 0.60 |
ASTM A 653M Z275 | ASTM A 653 G90 | 275 | 0.90 |
Storage
Regardless of the type of finish used, steel deck must be stored in a dry, well ventilated and waterproofed area. The contractor is responsible for taking the necessary measures to ensure that the steel decking and accessories are adequately stored from the time they are delivered to the site.
Impact of Connectors
Welds and connectors may cause local damage to the steel's protective finish. Oxidation of the steel may occur around the connector holes if the deck is in a humid or corrosive environment. It is possible to use connectors with rubber washers to protect the holes or to apply zinc-based primer over spot welds that have burned the finish.
Choice of Finishes for Steel Deck
* ASTM A 653M ZF75 finish must be field-painted prior to occupancy of the building. Measures must be taken to protect the steel deck upon delivery.
** Not all steel finishes are kept in stock; minimum volumes must be ordered and delivery dates must be approved. Contact a Canam sales representative for more information on delivery dates as well as available thicknesses and colours for specific finishes.
Conclusion
The majority of steel deck fabricated in Canada by Canam is galvanized steel. However, our equipment allows us to supply a variety of other finishes as required, depending on the volume and availability of the material. Since our priority is to meet your building needs, do not hesitate to contact a Canam sales representative regarding our various products and finishes.
References
Canadian Sheet Steel Building Institute
Dofasco |
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