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ch will lead eventually to formation corrosive environment within the crevice due the anodic imbalance.

The previous pictures shows crevice corrosion caused by the penetration of water through the seal of the GPS antenna to the fill the cracks and initiate crevice corrosion, as soon as the process started, the contact between the two parts of the structure became weak and more water penetrated. The rivets were found to be deteriorated and popped.

案例研究:荷兰的一个游泳池的屋顶坍塌-Case Study: Collapse of a swimming pool roof in the Netherland

Last year, a pool roof collapsed in the Netherlands; sadly taking the lives of many people. A similar accident in 1985, which was a fatal accident that took the lives of 12 people because of the collapse of the roof of a swimming pool in Switzerland as the concrete roof of the pool felled in after only 13 years of service. The authorities said that the main reason of collapse was the failure of a stainless steel rod hanger, which when failed created sudden extreme load on the other hangers that they didn't withstand and thus the whole roof collapsed.

The reasons of such accidents are caused because of closed pools environments. In such pools, the number of bathers is high especially in vacations, which will lead to the increase of contaminants generation to the water from human bodies. In order to meet the hygienic requirements; more sterilizing chemicals are added to the water. These chemicals contain high quantities of chlorine. When chlorine reacts with the generated contaminants it produces chloramines, along with the relatively high temperature of water and atmospheric air within the enclosed area, it creates the perfect conditions for attacking stainless steel. With the turbulence pool water motion, the rates of splash and thus vaporizing are very high in closed pools, creating a moist atmosphere, when these vapors cool down; they tend to condense on stainless steel surface creating the perfect conditions for corrosion; mentioning that chloride is an active corroding material that attacks reinforced concrete.

The combined effect of the previously mentioned factors led to deterioration of stainless steel hangers, authorities claimed that the main reason for this tragedy was 'Chloride-induced Stress Corrosion Cracking' which started when one or more of the hangers were pitted, creating the perfect conditions of SCC to be initiated which are tensile stresses due to the operating load and the residual stresses due to manufacturing plush the chemical corrosion factors by chlorine based compounds. As the crack reached a certain level; it leaded to mega fracture in the hanger rod, this fracture led to increasing the load on the other hangers, which were struggling with the same problem, and eventually led to the fracture of all of the hangers and sadly collapse of the roof.

The later conducted studies showed that SCC occurs in swimming pools due to three main reasons:

The use of sensitive types of stainless steel that can be easily affected by harsh conditions.

Tensile strengths subjected to the structure either because of the operating weight left stresses or internal stresses within the material created during manufacturing or installation.

The extensive existence of chlorine compounds in such environments which can easily be transported by water vapor or tiny wat