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1、1DRAFT(5.54)WATER BASED INORGANIC ZINCS PERFORMANCE VS PRACTICABILITYAuthors: Ern Hemmings and Nourhan Demirdjian.1. INTRODUCTION:There are currently a number of significant events being played out in the Australian Corrosion Protection Industry all related to inorganic zinc specification and usage.
2、 The first is the formation of the Zinc Rich Coatings Promotional Council with membership of the paint companies, zinc dust manufacturers, some other raw material suppliers and coating application associations. The formation of this group is quite remarkable in the Australian situation where paint c
3、ompanies have been more competitive than cooperative. We probably have to thank the APMF (Australian Paint Manufacturers Association) for initiating this group. Secondly there is considerable disagreement between the Galvanizing Industry Association representatives and those of the paint companies o
4、n the committee dealing with the revision of AS/NZS2312 Standard for Protecting Steel in Atmospheric Environment. The disagreement centres around the life expectancy to first maintenance for inorganic zinc coatings and galvanising. A third factor in this whole scene is the current recession in the g
5、lobal economy which has led to the demise of Pasminco the sole zinc producer in Australia. It has also led to the reduction in prices for hot dip galvanising as Australian galvanisers have competed against imported galvanised steel. Likewise engineering consultancies have looked for lower cost syste
6、ms as the investment in new resource projects have sought to keep the cost of capitalisation low to make projects viable in a market with low commodity prices. And fourthly there has been a significant change in the source of technical specifications to the Australian paint industry. I suspect that
7、this is a worldwide phenomenon driven by outsourcing of technical expertise in large chemical and mining companies. Very few now have their resident coatings or corrosion expert. Likewise paint companies have reduced their technical costs by reducing technical staff. Globalisation has also led to ce
8、ntralisation of research and development personnel in European or American sites with a consequent decrease in the understanding of the chemistry of coatings here in Australia. Another factor has been the constriction in the Australian Blast Cleaning and Coating Industry. Employees have been drastic
9、ally reduced and a number of companies have closed their doors. Associations like the BCCA and AIPC have never been weaker in supporting their industry. In summary the industry has changed considerable over the last 5 years. The results of those changes is the current unsatisfactory situation with r
10、egard to inorganic zinc specifications.2.CURRENT SITUATION AND HOW WE GOT THERE:The current situation with regard to inorganic zinc coatings is as follows. Where heavy duty coatings are required in a marine environment and where aesthetics are not a significant issue then there is a preference by co
11、ating consultants to specify a single coat of high ratio water based inorganic zinc coating. This is usually to a dry film thickness (DFT) of either 100 150 microns or a minimum of 150 microns.2This system originated with the entry to the coatings industry in the USA of a company called Inorganic Co
12、atings. This company acquired the rights to a 1979 NASA patent for the production of what was called “High Ratio “ water borne inorganic zinc coatings. The NASA patent essentially took the existing self- curing alkali silicate technology that had been around since the 1960s and with the use of collo
13、idal silica increased the ratio of silicate to alkali metal composition in the silicate binder. The result of this advance was to produce a water based silicate binder for zinc powder that achieved film hardness and water insolubility faster and enabled the application of thicker films in one coat.
14、Although the owners of Inorganic Coatings were not great chemists they were exceptional marketers and with phrases such as “instant cure” and “lifetime protection” managed to convince the industry that they had developed a new coating that would revolutionise the corrosion protection industry. Sever
15、al factors were in their favour; one being the emergence of the environmental legislation in the USA, restricting the use of solvent based coatings. The 100% water content of “High Ratio Inorganic Zincs” gave them a receptive audience. In addition they enlisted the services of “Chuck” Munger of Amer
16、on fame to promote the benefits of this product. (1) For clarity we should point out that an arbitrary figure has been chosen in the AS/NZS3750.15 standard of a mole ratio of minimum 4.7:1 silica to alkali metal ratio as defining “high ratio” or Type 6 products. In this paper we are refering to such coatings as conform to this definition. This technology was brought to Australia through two avenues. Valspar Coatings took up a license to sell but not manufacture the coatings and Taubmans,
