cost analysis

Using data collected in nationwide surveys of the hot-dip galvanizing industry (conducted by the American Galvanizers Association) and the paint industry (conducted by the National Association of Corrosion Engineers), an economic analysis of original and life-cycle costs provides an interesting comparison.

Original Costs

Although not recommended as reflecting the true cost of a corrosion protection system, original costs are sometimes the primary determinant for selection. As can be seen in the figure below, the original cost of hot-dip galvanizing is compared to four typical paint systems. Hot-dip galvanizing is more economical from an initial cost standpoint for all but the one-coat zinc-rich paint and the two-coat acrylic waterborne paint. This is the case when galvanizing is compared to many of the commonly used industrial paint systems. Additionally, hot-dip galvanizing may be even more economical when the project calls for small-weight-per-beam-length structural steel and/or assemblies, because of the efficient handling of many pieces in the galvanizing process.

Life-cycle Costs

Because of the long life of the hot-dip galvanized coating and its virtually maintenance-free performance, galvanizing is consistently a better value than paint over the life of the structure. Galvanizing durability and lifetime performance make it the logical choice when it is the lowest original cost system. However, as the material's weight-per-beam-length increases, galvanizing may be initially more expensive than some paint systems. In these cases, life-cycle cost information must be examined to discover the true value of hot-dip galvanizing.

Life-cycle cost is the analysis of the true cost of a coating system over its entire service-life. It considers original costs, touchup costs, maintenance costs, repainting costs, inflation, and opportunity costs. So, using the standard formula for the time-value of money, the true cost in present day dollars (NPV) is calculated as:

Galvanizing is considerably more economical over the lifetime of a project than even the simplest one- or two-coat paint systems, as is strongly demonstrated in the above figure. If the practical maintenance cycle for paint is not strictly adhered to, life-cycle costs could be significantly higher than those presented in the figure above.

Figure 1 Notes:

1. U.S. Dollars
2. Galvanizing data from 2001 nationwide industry survey
3. Paint data from 1998 NACE Paper #509
   5% increase in paint material cost/year since 1998
   3% increase in paint preparation cost/year since 1998
4. Maintenance repaint at 5% rust, moderately industrial environment, practical maintenance cycle

The qualitative analysis of various corrosion protection systems indicates hot-dip galvanizing to be the premier choice. It is a durable barrier and cathodic protection system with a metallurgical bond an order of magnitude greater than that of paint. The galvanized coating provides complete coverage inside tubular sections and in hard-to-reach places. It provides uniform thickness and protection on edges and corners and is abrasion resistant. When all of these performance characteristics are considered in conjunction with low original and life-cycle costs, hot-dip galvanizing is the logical choice.

Click to review case studies where hot-dip galvanizing was chosen over other corrosion protection systems due to the life-cycle cost.

 ^ back to top