# A Novel Accelerated Corrosion Test for Supporting Devices in a Floating Photovoltaic System
## 4 Conclusions  
The visual observation of five types of screw fastened in SUPERDYMA shape steel using the CASS test hasdemonstrated that the surface of SUPERDYMA shape steel was almost completely covered by a white protective layer, but a local region had already rusted. This result indicates that most of the surface of the SUPERDYMA shape steel was resisted corrosion, while only a partial area of the white protection layer was fully corroded and further rusted into the ground layer steel. We observed the heads and tails of five types of screws with varying degrees of rust. Type 316 SS had the highest corrosion resistance, followed by type 304 SS and type 410 SS. The chromate-passivated galvanized steel screw had a better corrosion resistance than the general galvanized steel screw because of the contribution of a chromium-containing chemical conversion coating. The XP zinc-tin alloy  
Figure 8: The appearance of an XP zinc–tin alloy coated steel screw/bolt/nut after the eight-day CASS test (192 h): (**a**) screw head, (**b**) screw tail, (**c**) bolt head, (**d**) bolt tail, and (**e**) nut.  
Figure 9: The appearance of a XP zinc–tin alloy coated steel screw (upper row) and the galvanized steel screw capped with a type 316 SS nut (lower row) after a 136-day NSS test.  
coated steel screw produced numerous yellow protection layers instead of red rust to prevent further corrosion. Furthermore, the corrosion results of the XP zinc-tin alloy coated steel screw and galvanized steel screw capped with a 316 SS nut revealed that the corrosion degree of the eight-day CASS test was more significant than that of the 136-day NSS test. Therefore, the CASS test is a faster and more efficient method for evaluating the durability of the supporting devices. It is an accelerated corrosion method that needs more research, for example through a comparison of the corrosion weight loss, corrosion potential, and potentiodynamic polarization parameters between the CASS test, NSS test, cyclic corrosion test (CCT), and field exposure test.  
Environmental conditions on the surface of water are harsher than on the ground; however, regulations and standards relevant to the application of supporting devices in FPV systems are currently insufficient. Users can only rely on the test data provided from manufacturers or agents to estimate the lifetime of supporting devices, or unilaterally believe the uncertified warranty of supporting devices that manufacturers or agents provide. Currently, FPV systems in Taiwan are planned to be installed on water areas, such as reservoirs, lakes, and fish farms, and there are a lack of data to evidence whether the supporting devices are safe enough to use enduringly. As consequence, both the safety and durability of supporting devices in FPV systems are urgent issues that need to be resolved if a government is planning on positively implementing green energy and installing FPV widely. Standard test methods for supporting devices in FPV systems must be established as soon as possible, and the minimum requirements of supporting devices must be evaluated in order to enhance the minimum service life further, reduce the risk of damage to supporting devices, and reduce the overall maintenance costs.  
Conceptualization, C.-K.L.; methodology, C.-K.L.; validation, C.-K.L.; formal analysis, Z.-R.K.; data curation, C.-K.L.; writing--original draft preparation, C.-K.L. and Z.-R.K.; writing--review and editing, M.-J.K.; visualization, C.-K.L.; supervision, M.-J.K.; project administration, T.-C.W.; funding acquisition, T.-C.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Bureau of Energy, the Ministry of Economic Affairs (grant number 107-D0307).  
Not applicable.  
The authors declare no conflict of interest.