Steel Protection
By Hot Dip Galvanizing & Duplex Systems
Information courtesy of: HOT DIP GALVANIZERS ASSOCIATION SOUTHERN AFRICA
Foreword
This edition of "Steel Protection by Hot Dip Galvanizing & Duplex Systems" has been completely revised and updated to include the newly adopted ISO specifications for hot dip galvanizing. This includes the specifications applicable to the galvanizing of tubes by the semi-automatic process. In addition, more comprehensive information has been added to the sections covering wire and continuously galvanized sheet. The latter provides the latest available information on prepainted sheet products available in South Africa.
The inspection of hot dip galvanized articles and their expected performance in a range of environments is critical to the successful application of hot dip galvanizing in corrosion control. This guide provides ample support for the specifier, designer and user to utilise the unique combination of properties of hot dip galvanizing when applied to steel. As in other editions, information in the guide is based upon scientific literature supported by the invaluable experience of various experts, locally and overseas.
This is the 5th edition available in South Africa and the 2nd edition totally written solely for this market. Based upon earlier editions provided from overseas, the contribution of the authors of these editions is acknowledged and greatly appreciated.
Members of staff of The Hot Dip Galvanizers Association of Southern Africa are always available to provide further support and advice on the design, application and performance of hot dip galvanizing. Please feel free to contact us.
For long service maintenance free corrosion protection, specify hot dip galvanizing for conveyor line steel work. This conveyor line has been exposed to the environment at hand for 15 years. Hot dip galvanized components still have 80 to 120 m of coating protection. Other coatings on idler frames and all fasteners hove failed and require maintenance. Inset shows the conveyor line when new.
Table of Contents
| 1 |
About Corrosion and Rust Prevention |
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| 2 | Choice of Rust Prevention Method | |
| 3 | Corrosion Protection Methods | |
| 3.1 | Hot Dip Galvanizing | |
| 3.2 | Electroplating | |
| 3.3 | Zinc Metal Spraying | |
| 3.4 | Sherardizing | |
| 3.5 | Mechanical Plating | |
| 3.6 | Coating with Zinc-Rich Paint/Epoxy | |
| 4 | Hot Dip Galvanizing | |
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4.1 |
The Advantages of Hot Dip Galvanizing | |
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4.2 |
The Disadvantages of Hot Dip Galvanizing | |
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4.3 |
The Hot Dip Galvanizing Process | |
| 5 | Hot Dip Galvanizing of Sheet Metal |
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5.1 |
Zinc Coating Surface Finish |
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5.2 |
Surface Treatment |
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5.3 |
Cut Edge Corrosion Resistance |
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5.4 |
Strain Ageing |
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5.5 |
Painting |
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5.6 |
Primer Coated Galvanized Steel Sheet Produced in a continuous coating Line (CHROMAPREP) |
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5.7 |
Painted Cold Rolled Galvanized Steel Sheet Produced in a Continuous Coating Line (CHROMADEK or CHROMADEK PLUS) |
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5.8 |
Fastening Methods |
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5.9 |
The Handling and Protection of Galvanized and Prepainted Steel Sheet During Storage |
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| 6 |
Hot Dip Galvanizing of Wire |
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6.1 |
The Process |
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6.2 |
Practical Aspects |
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| 7 |
The Reactions Between Iron and Zinc |
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7.1 |
Composition and the Metallurgy of the Steel |
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7.2 |
Zinc Temperature |
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7.3 |
Immersion Time |
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7.4 |
Alloying Additions to the Molten Zinc |
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7.5 |
The Withdrawal Rate of the Article from the Molten Zinc |
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7.6 |
Surface Condition |
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7.7 |
Thickness of the Steel |
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7.8 |
The Iron/Zinc Reaction in Continuous Galvanizing |
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| 8 |
Mechanical Properties of Hot Dip Galvanized Steels |
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8.1 |
Strength and Ductility |
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8.2 |
Embrittlement |
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8.3 |
Fatigue Strength |
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| 9 |
Design for Hot Dip Galvanizing |
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9.1 |
Introduction |
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9.2 |
Venting. Filling and Drainage |
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9.3 |
Masking, Welding, Handling, Minimizing Distortion, Clearance for Moving Parts and Identification |
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9.4 |
Packaging and Transporting of Hot Dip Galvanized Goods |
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| 10 |
Specifying Hot Dip Galvanizing |
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10.1 |
Hot Dip Galvanizing Specifications |
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10.2 |
Lead Times |
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| 11 |
Quality - Inspection Before and After |
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11.1 |
Inspection Before Hot Dip Galvanizing |
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11.2 |
Inspection After Hot Dip Galvanizing |
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11.3 |
Thickness Testing |
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11.4 |
Appearance |
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11.5 |
Adhesion of the Coating |
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11.6 |
Testing for Adhesion |
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| 12 |
Corrosion Resistance of Hot Dip Galvanized Coatings |
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12.1 |
Corrosion Resistance in the Atmosphere |
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12.2 |
Wet Storage Stain |
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12.3 |
Galvanic Corrosion |
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12.4 |
Corrosion Resistance of Hot Dip Galvanized Coatings in Aqueous Conditions |
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12.5 |
Corrosion Resistance of Hot Dip Galvanized Coatings in Soil Conditions |
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12.6 |
Hot Dip Galvanized Steel in Contact with Building Materials |
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12.7 |
Abrasion Resistance of Hot Dip Galvanized Coatings |
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12.8 |
Hot Dip Galvanized Coatings Exposed to Elevated Temperatures |
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| 13 |
Bolted Connections |
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13.1 |
Type of Structural Bolts and Fastening Devices |
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13.2 |
Corrosion Prevention | |
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13.3 |
Corrosion Resistant Metals | |
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13.4 |
Protective Coatings | |
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13.5 |
Hot Dip Galvanizing of Fasteners | |
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13.6 |
Bolt and Nut Assemblies | |
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13.7 |
Washers | |
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13.8 |
Re-Use of High Strength Fasteners | |
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13.9 |
Bolt Tensioning Procedures | |
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13.10 |
The Effect of Hot Dip Galvanizing on Strength Properties of Fasteners | |
| 14 | Welding of Zinc-Coated Steel | |
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14.1 |
Shielded Metal Arc Welding (SMAW) | |
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14.2 |
Gas Metal Arc Welding (GMAW) | |
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14.3 |
Gas Tungsten Arc Welding (GTAW) | |
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14.4 |
Flux Cored Arc Welding (FCAW) | |
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14.5 |
Submerged Arc Welding (SAW) | |
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14.6 |
Oxyfuel Gas Welding (OGW) | |
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14.7 |
Brazing and Braze Welding | |
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14.8 |
Soldering | |
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14.9 |
Embrittlement of Steel by Liquid Zinc During Arc and Oxyfuel Gas Welding | |
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14.10 |
Resistance Welding | |
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14.11 |
Safe Health Practices | |
| 15 | Reconditioning Damaged Or Site Modified Hot Dip Galvanized Coatings | |
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15.1 |
Coating Repair Procedure by the Galvanizer | |
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15.2 |
Site Repairs | |
| 16 | The Cost Effectiveness of Hot Dip Galvanizing | |
| 17 | Painting of Hot Dip Galvanized Steel - Duplex Systems | |
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17.1 |
When to Paint Hot Dip Galvanized Steel Structures | |
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17.2 |
Surface Preparation for Duplex Coating | |
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17.3 |
System Selection | |
