GALVANIZED COATING BASICS AND TUTORIALS

GALVANIZED COATING BASIC INFORMATION
What Is Galvanized Coating?

The galvanizing process produces a durable, abrasion-resistant coating of metallic zinc and zinc-iron alloy layers bonded metallurgically to the steel base and completely covering the work piece.

No other coating for steel matches galvanizing’s unique combination of properties and advantages:

1. For most classes of steelwork, galvanizing provides the lowest long-term cost. In many cases galvanizing also provides lowest initial cost.

2. The galvanized coating becomes part of the steel surface it protects.

3. The unique metallurgical structure of the galvanized coating provides outstanding toughness and resistance to mechanical damage in transport, erection and service.

4. The galvanized coating is subject to corrosion at a predictably slow rate, between one-seventeenth and one-eightieth that of steel, depending on the environment to which it is exposed.

5. Galvanizing’s cathodic protection for steel ensures that small areas of the base steel exposed through severe impacts or abrasion, are protected from corrosion by the surrounding galvanized coating.

6. An inherent advantage of the process is that a standard minimum coating thickness is applied.

7. During galvanizing the work is completely immersed in molten zinc and the entire surface is coated, even recesses and returns which often cannot be coated using other processes. If required, internal surfaces of vessels and containers can be coated simultaneously.

8. Galvanized coatings are virtually ‘self-inspecting’ because the reaction between steel and molten zinc in the galvanizing bath does not occur unless the steel surface is chemically clean. Therefore a galvanized coating which appears sound and continuous is sound and continuous.

9. Galvanizing is a highly versatile process. Items ranging from small fasteners and threaded components, up to massive structural members can be coated.

10. The mechanical properties of commonly galvanized steels are not significantly affected by galvanizing.

11. Galvanizing provides outstanding corrosion performance in a wide range of environments.

12. ‘Duplex’ coatings of galvanizing-plus-paint are often the most economic solution to the problem of protecting steel in highly corrosive environments. Such systems provide a synergistic effect in which the life of the combined coatings exceeds the total life of the two coatings if they were used alone.

STEEL STRUCTURES ERECTION EQUIPMENT CIVIL ENGINEERING TUTORIALS

STEEL STRUCTURES ERECTION EQUIPMENT TUTORIALS
What Are The Steel Structure Erection Equipment?

If there is a universal piece of erection equipment, it is the crane. Mounted on wheels or tractor threads, it is extremely mobile, both on the job and in moving from job to job.

Practically all buildings are erected with this efficient raising device. The exception, of course, is the skyscraper whose height exceeds the reach of the crane.  Operating on ground level, cranes have been used to erect buildings of about 20 stories, the maximum height being dependent on the length of the boom and width of building.


The guy derrick is a widely used raising device for erection of tall buildings. Its principal asset is the ease by which it may be ‘‘jumped’’ from tier to tier as erection proceeds upward. The boom and mast reverse position; each in turn serves to lift up the other.

It requires about 2 h to make a two-story jump. Stiff-leg derricks and gin poles are two other rigs sometimes used, usually in the role of auxiliaries to cranes or guy derricks. Gin poles are the most elementary— simply a guyed boom.

The base must be secure because of the danger of kicking out. The device is useful for the raising of incidental materials, for dismantling and lowering of larger rigs, and for erection of steel on light construction where the services of a crane are unwarranted.

Stiff-leg derricks are most efficient where they may be set up to remain for long periods of time. They have been used to erect multistory buildings but are not in popular favor because of the long time required to jump from tier to tier.

Among the principal uses for stiff legs are (1) unloading steel from railroad cars for transfer to trucks, (2) storage and sorting, and (3) when placed on a flat roof, raising steel to roof level, where it may be sorted and placed within each of a guy derrick.

Less time for ‘‘jumping’’ the raising equipment is needed for cranes mounted on steel box-type towers, about three stories high, that are seated on interior elevator wells or similar shafts for erecting steel.

These tower cranes are simply jacked upward hydraulically or raised by cables, with the previously erected steel-work serving as supports. In another method, a stiff-leg derrick is mounted on a trussed platform, spanning two or more columns, and so powered that it can creep up the erected exterior columns.

In addition to the advantage of faster jumps, these methods permit steel erection to proceed as soon as the higher working level is reached.