Galvanized Steel Protective System Assessing: Comparison of Neutral Salt Spray Test and Customized Accelerated Ageing Atmospheric Test

摘要

All the components being part of overhead electrical network undergo changes of climatic conditions leading to atmospheric corrosion. Preventive measures adapted to local environment corrosivity, as use of galvanized steel, are taken to ensure service lifetime of the system For example, for electric insulators, polluting particles agglomerate more on enclosed areas where they are not ventilated by wind blow or on areas with high electric activity. These pollution agglomerates lead to a local accelerated corrosion phenomenon. Applying a protective paint on this concerned zone is one of the solutions proposed to delay local degradation and therefore secure lifetime. The aim of this study is to assess painting efficiency using two tests and comparing results of both. A two-layer painting system has been selected and applied on a large quantity of objects. Some are tested under neutral salt spray (normalized test), others are tested using a method consisting in impregnating the surface with salts by dipping in saturated sodium chloride solution and exposure in climatic chamber, with specific temperature and relative humidity cycles. At the end of both tests, painting blistering is observed and pulverulent products appear under painting. Top coating cracked because of the swelling due to underneath products. These products are the results of the reaction between primer and environment. While underneath galvanized steel is still clean on objects after unnormalized test, degradation initiates after neutral salt spray. Partial painting of objects and their disposition made the contact between solution and primer possible by percolating and infiltration. Learning from this study is the care in placing objects during tests and the very marked aggressiveness of normalized neutral salt spray compared to customized accelerated ageing atmospheric test.