A Comparison of Australian and International Design Standards and Codes for Cathodic Protection Systems

摘要

The design of a cathodic protection system is a relatively simple process, provided the data required to design the system is available. As a structure owner trying to have a system designed and installed, merely referring to Standards may not guarantee you a system that is best for your application. Reviewing the standards which have been considered in this paper, it appears that it is common practice for standards to refer to relevant standards originating from overseas, or to at least acknowledge these standards. This is not currently generally the case in Australia for most of the Australian and NACE Standards, and to many people, the foreign standards which are used are not known. As can be seen from the examples of the pipeline system sacrificial design, there is a significant difference in the mass of anode installed between the most conservative and least conservative standard used, and somewhere in between the correct answer lies. It is also apparent that the more recent the Standard, the less conservative the design values. Whilst this is the case in general, there are factors which some of the better known and used standards do not adequately address. Effects such as the accelerated anode consumption at the end of line, where anodes due to their lower resistance, are depleted prior to anodes on neighbouring structures. This is only now starting to be considered in some of the revisions which are currently being drafted. The effects of temperature and deewater on current requirements and anode compositions are also now being addressed in the latest revisions and drafts. In terms of what we have to work with, when you examine the amount of information that is included as guidelines and data in the Australian Standards, there is an extensive technical resource which is provided for the owners of a structure which is going to be cath-odically protected. The standards do however stop short of enabling designers to come up with "consistent" and comparable systems. NACE have in recent years established the World Corrosion Organisation to attempt to bring that various Associations around the world closer together. Interestingly, one of the "goals" of the World Corrosion Organisation is:- "To normalize corrosion-related standards worldwide: to harmonize the standards that are already in use." With time, we may see a closer relationship with the various standards, to the benefit to the industry and asset owners.