Are Galvanized Products Cost-Effective?
The debate on whether to apply spray or paint-on alternatives as corrosion preventatives versus the hot-dipped galvanization process is as fierce as ever. Many procurement personnel in the construction and industrial sectors still base their costings of rust prevention procedures on immediate direct costs without investigating long-term maintenance expenditure.
Factoring in the Facts
It is a well-documented fact that doing nothing to treat steel has devastating effects on the material over just a few years. The choices to mitigate the resulting oxidation are, to treat the material with either spray or paint-on rust preventative products or to have the metal treated by using the hot-dipped galvanization process.
Steel products have been protected by zinc metal through the hot-dip galvanization process for 250 years and it is equally well-documented that a well-galvanized steel product has a life span of between 50 and 75 years with little to no maintenance. The base price of zinc has also remained relatively stable against inflation over the last twelve years.
Calculating the Cost of Galvanization
What is not taken into account is that the galvanization process is not very labour-intensive whereas alternative procedures are. Galvanized steel will need little to no maintenance for decades whereas other products will. These facts illuminate the difference between short-term solutions and long-term investments.
The short-term solution does not take into account inflation, increases in rust protection product prices, increased labour costs and equipment for application investments like scaffolding, safety gear and the covering of machinery within the structure, for example. But most importantly, consequential loss in productivity and profits is not accounted for when the premises needs to be shut down for the duration of the maintenance.
Checking the Facts with Science
Hot-dipped galvanization protects steel from corrosion in three ways:
- Cathodic – Zinc is more anodic than steel. In Layman’s terms, when a corrosion cell is formed at a molecular level between zinc and steel, the zinc gives up electrons to protect the steel from corrosion. Thus, zinc will protect the base metal, even if damaged, until all the zinc coating is consumed.
- Barrier – Zinc is a very dense metal. As a result, it does not allow moisture to penetrate the hot-dipped coating and therefore protects the base steel.
- Patina – Immediately after the galvanizing process, through the first few months the hot-dipped zinc outer coating is exposed to oxygen, water molecules and then carbon dioxide. It eventually forms a thin film of zinc carbonate which is a passive patina film. This film then binds tightly with the remaining zinc in the galvanized coating forming an impermeable barrier, giving it its reputable durability.
Additionally, sulphur and chloride emissions, previously emitted by motor vehicles, power plants and heavy industry increase corrosion rates in all metals, including zinc. Since environmental changes have been made by the producers of these sources over the past 20 years and emission rates have decreased, a 2001 study found that galvanised steel will now last even longer than in previous decades.
In comparative studies, a worksheet example analysed the cost of galvanized steel and was compared to painting it with a two-coat paint application procedure (inorganic zinc primer and polyurethane topcoat). In the current environmental conditions at the project site and based on a facility life of 30 years, the hot-dipped galvanized steel was not only more economical upon initial investment but over the projected lifecycle of the project, it was five times more cost-effective in comparison to the painted procedure.
How to Invest in Longevity
For premium service, best advice and leading galvanized products, consider Armco Superlite. We have two cutting-edge galvanizing plants in Johannesburg. Our flagship facility in Isando has been operating since 1989 and is geared to accommodate heavy structural steel of up to 13m long at an expected output of approximately 2000 tons per month. Our second facility in Randfontein boasts an average output of 800 tons per month and accommodates light to medium structural steel of up to 6m long. For innovative solutions and cutting-edge technology, be armed with Armco.
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