A rational approach to cost comparisons of various protective coatings

摘要

Cost comparisons between hot dip galvanizing and organic coatings tend to be difficult as galvanizing is quoted in costs per tonne, whereas organic coatings are quoted in costs per square metre. In addition, there are difficulties in converting the figures as structural steel is considered to be light, medium or heavy depending upon the tonnes per square metre of surface. Although cost comparisons for various corrosion protection systems are carried out from time to time, it is necessary to look at studies where international comparisons can be made. This study was commissioned to provide an agreed method of cost comparison by having all the participating parties agreeing upon the basis for calculation. Using the ISO 9223:1992 Corrosion of metals and alloys - Corrosivity of atmospheres - Classifications, recommendations of coatings to be applied were provided by various coatings suppliers. Guidance for this was taken from SABS ISO 12944 Paints and varnishes - Corrosion protection of steel structures by protective paint systems. Part 5: Protective paint systems. This information was then circulated to coatings applicators countrywide to obtain the applied costs for the various coatings. This paper discusses the procedures carried out and is given as a method to obtain costings from various competing systems with the co-operation of all. The information provided is invaluable to the steel fabricator in providing information on the optimum corrosion protection system to be employed in particular environments. This should enable cost-effective decision-making and allow for the corrosion protection system to take its rightful place in the design and installation phase of structural steel projects.