Coated Sheet 


Electrolytic Zinc Coated and Zinc-Iron Alloy Coated Sheet
Fabrication Considerations

Joining  |  Sealants  |  Painting

Forming
Electrogalvanized sheet can be formed in a variety of ways, from simple bending to complex operations involving combined deep drawing and stretching.

Although the steel substrate for electroplated sheet has mechanical properties similar to cold rolled sheet, the characteristics of the zinc and zinc-iron coatings have considerable influence on the sheet's performance during forming operations. For example, the surface finish and relative softness of pure zinc coatings, compared with uncoated cold rolled steel sheet, cause differences in frictional behavior in dies. Thus for optimal forming, it is generally advantageous to use dies that are harder and smoother for electrogalvanized sheet than those used for cold rolled sheet. Other forming parameters, such as die clearances and hold-down forces, also may have to be adjusted. Because the zinc-iron alloy coating is significantly harder than a pure zinc coating, there is usually not as much adjustment needed for this product. In some cases, lubricants that are effective with uncoated cold rolled sheet of similar metallurgical quality perform less satisfactorily with electrogalvanized sheet. Therefore, care must be exercised in choosing forming lubricants.

Joining

Welding
Electrogalvanized sheet can be readily welded by the resistance, arc and oxyfuel gas welding processes, usually with the same equipment used to weld the uncoated underlying steel. Joining and safety precautions are similar to those described for hot-dip galvanized sheet. Because of lower surface contact resistance, the welding parameters must be adjusted for electrogalvanized sheet to achieve successful resistance welding. Spot welding of electrogalvanized sheet has been thoroughly developed by the automotive industry and is being used extensively in assembly plants.

Electrogalvanized sheet also has two features that allow consistent spot weldability. First, the exceptionally uniform coating thickness achieved by electrogalvanizing allows fine tuning of the welding operation with assurance of good results that can be reproduced time after time. Second, electrogalvanized sheet users often specify relatively thin coatings since thinner coatings enhance electrode life.

Soldering
Electrogalvanized sheet can be readily soldered with many types of conventional solders and fluxes. Flux residues should be removed after soldering to prevent corrosive damage to the coating. Materials and methods similar to those used to solder hot-dip galvanized sheet can be employed.

Adhesive Bonding
Adhesive bonding is a proven technique that can join steel effectively to many materials. It can also improve product design and performance. Electrogalvanized sheet can be fastened readily by adhesive bonding in the same way and with the same adhesives as hot-dip galvanized sheet.

Sealants
Sealants are often used between overlapping areas of steel sheet to form watertight joints and to achieve superior environmental durability. Neutral-cure silicone rubber sealants are recommended for use with electrogalvanized sheet. These materials need no primer. They are flexible, non-corrosive and resistant to heat, cold, water and ultraviolet rays.

Other types of sealants, like butyl rubber and styrene butadiene rubber, may also be considered for certain applications. For more information about sealants for specific applications, consult a sealant manufacturer.

Painting
U. S. Steel Electrogalvanized Sheet can be readily painted to develop good paint adhesion, high corrosion resistance and a quality surface finish. Although most experience in painting U. S. Steel Electrogalvanized Sheet has been with automotive postpainting systems (after fabrication and assembly), the technology for coil line prepainting (before fabrication) is well known (prepainted coated sheet). Excellent paintability and corrosion resistance are achieved by the automotive industry when electrogalvanized sheet is applied for exposed body panels. Automotive paint technology is very advanced today, and painting over metallic-coated steels is very successfully done on a routine basis.

Typical Applications Application Considerations Fabrication Considerations Tolerances