Electrogalvanizing of steel

Corrosion protection, including deposition of metal coatings such as electrogalvanizing of steel with zinc and electrophoretic deposition of insulating films, both of which are industry standards for protection of automotive bodies... 

Industrially, the most important property of zinc metal is its ability to form an alloy with iron so that a thin adherent layer can be applied to the surface of iron workpieces. The zinc coating, obtained either by hot-dip galvanizing or aqueous electrogalvanizing, considerably extends the service life of steel constructions. In addition, zinc alloys can be easily cast into intricate shapes that are used extensively in household goods and automotive equipment, building, and construction utilities. Other important areas are brasses, batteries, tires, and other rubber goods. Furthermore, zinc is now known to be an essential nutrient that is indispensable for human health as well as for many species of animals and plants, and it is therefore used in pharmaceuticals, fertilizers, and animal feed. 

Lap joints of electrogalvanized 1006 low-carbon steel to 6111 aluminum that is spot welded with electrogalvanized 1006 steel-clad S0S2 aluminum (60 to 40 ratio) transition... 

FIGURE 14.7 Illustration of dielectric heating for the bonding of an electrogalvanized steel (EGS)/ SMC lap shear joint.30... 

Figure 52 Normal current density distribution over a scribed electrogalvanized steel sample in 0.01 M NaCl as a function of time (a) 15 min, (b) 1 h, (c) 2 h. (From H. S. Isaacs, A. J. Aldykewicz, D. Thierry, T. C. Simpson. Corrosion 52, 163 (1996).)...

Figure 1. Lap-shear strength (top) and T-peel strength (bottom) of one-part epoxy adhesives (Adhesive A formulations). Key CRS, oily cold-rolled steel EGS, electrogalvanized steel CTy control (unmodified resin) T-Ay T-By and T-C refer to particle sizes of MEAc tougheners 5 to 45 pm (T-A)y 17.8 pm (T-B), and 2.3 pm (T-C) and L13y Hycar CTBN (1300x13).

A major problem in automotive vehicles is corrosion control, particularly in the northern areas of the country where salts are used to melt road ice. Protection of exposed steel from corrosion is accomplished by electroplating with copper-nickel-chromium films, particularly on trim and finish moldings. Electrophoretic painting of body panels is used industry-wide, and electrogalvanizing to protect steel under paint is soon to become a standard practice for all vehicles. Electrochemical accelerated tests for the integrity of coatings and for the determination of the concentration of coolants are used extensively. 

Chemical process plants often use epoxy, acrylic, polyurethane, and other coatings to prevent corrosion.107 Food cans often have epoxy resin linings. A coating made by the plasma polymerization of a 1 1 perfluorobutane-hy-drogen mixture protected copper from aqueous corrosion.108 Auto makers often use electrogalvanized steel... 

One goal of the Partners program is to increase the teachers enthusiasm for chemistry so they will transfer their "chemistry excitement to their students. Runyan, for example, got some of his ideas for relating the concept of the chemistry of corrosion and reactions with metal from his work with Armco, Inc. Armco manufactures steel at its Middletown, Ohio, plant, which also includes a newly added electrogalvanizing line and is home to its corporate research facility. 

S. Kotowski and B. Busse. Titanium Anodes for Steel Strip Electrogalvanizing, In F. Mine, B.V. Tilak, J.M. Denton, J.D. Lisius (eds). Performances of Electrodes for Industrial Electrochemical Processes, The Electrochemical Society Inc., Pennington, NJ, 245 (1989). 

Dattilo, M. (1985). Polarization and corrosion of electrogalvanized steel—Evaluation of zinc coatings obtained from waste-derived zinc electrolytes. J. Electrochem. Soc., /52(H), 2557-2561. 

Varady, E. (1971). Comparison of the corrosion resistance of hot galvanized steel, zinc-sprayed steel and zinc plated (electrogalvanized) steel in urban industrial atmospheres. EGGA General Meeting, Cannes. Paper, available from EGGA. 

This process is sometimes mistakenly referred to as electrogalvanizing. In this process zinc salt solutions are used in the electrolytic deposition of a layer of zinc on a cleaned steel surface. 

Dattilo, M., "Polarization and Corrosion of Electrogalvanized Steel—Evaluation of Zinc Coatings Obtained horn Waste-Derived Zinc Electrolytes, Journal of the Electrochemical Society, Vol. 132, No. 11, 1985, pp. 2557-2561. 

Fedrizzi, L. Ciaghi, L. Bonora, P.L. Fratesi, R. Roventi, G. (1992) Corrosion Behaviour of Electrogalvanized Steel in Sodium Chloride and Ammonium Sulphate Solutions, a Study by E.I.S. /. Appl. Electrochem, Vol. 22, pp. 247-254, ISSN 0021-891X... 

FIGURE 7.2 Natural log of underfilm corrosion, as a function of drying ratio for cold-rolled steel, electrogalvanized (20 giro Zn and 40 giro Zn), and hot-dipped galvanized (90 g/vo Zn). Data from Ito, Y., Hayashi, K., and Miyoshi, Y., Iron Steel J., 77, 280, 1991. 

The weU-known ASTM B117 salt spray test provides a comparison of cold-rolled and electrogalvanized steel within several hundred hours. Unfortunately, the salt spray test is unable to predict the well-known superior corrosion resistance of galvanized relative to uncoated cold rolled... 

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