Steel Protection By Hot Dip Galvanizing & Duplex Systems

Information courtesy of: HOT DIP GALVANIZERS ASSOCIATION SOUTHERN AFRICA

The Cost Effectiveness of Hot Dip Galvanizing

The choice of rust prevention system is often made only on the basis of purchase price. However, the purchase price says little about the overall economy of the different rust prevention systems.

The maintenance costs of one system can be considerably higher than those of another. This is especially true if access to the structure is difficult; if maintenance causes operational stoppages; if products and machines have to be covered, or if scaffolding has to be erected.

Unfortunately, it is not practical to give a universally applicable answer to the cost of hot dip galvanizing or other surface treatments, Structures and components vary in size, which affects the ease with which they can be handled and therefore the cost of galvanizing.

The price of hot dip galvanizing is based on the mass of the goods, whereas the price of painting is usually based on the surface area (figure 102). The relationships between average material thickness and surface in m²/tonne are given in figure 100.

The initial costs are often generally lower for hot dip galvanizing than for painting (figure 101) because painting is more labour-intensive than hot dip galvanizing.

Figure 100. Diagram far re-calculation of material thickness in mm to material surface in m² per tonne. (According to H-J Bttcher and J P Kleingarn)

When the total costs of different rust prevention systems are to be compared, a number of complications become evident, since intervals between individual maintenance requirements can vary. The cost situations at each such interval can also vary. However, the long service life given by zinc coatings, together with the reduced risk of minor damage leading to a significant reduction in protection against corrosion, almost always makes hot dip galvanizing cheaper than other methods of surface treatment in the long run.

Total lifetime costs of corrosion prevention systems vary because of different service intervals, different labour contents, the complexity of the maintenance task access costs and discount rates used in present value calculations. The first cost of galvanizing will often be higher than the first cost of short life paint systems but lower than long life paint systems. The cost of hot dip galvanizing complicated shapes and fabrications with high surface to weight ratio will usually be more competitive than the cost of painting. Hot dip galvanizing will also offer short turn round times with no danger of costly site delays. These factors, plus long service life, will usually lead to corrosion protection by hot dip galvanizing being an extremely competitive engineering solution.