Installing Solar Electric Since 1983

 

Corrosion of PV Modules and Racking in a Marine Environment

This case study is a work in progress. Last edited 6/2/15. Check back for updates. Click on any image for an enlarged version.

Background: In 2006 we were contracted to install a grid-tied solar-electric system on the roof of a beach-side cottage in Southern California. The system was comprised of Solar World modules on Direct Power and Water aluminum frame racking and one SMA string inverter. The PV was bolted to the tilt-up racking with stainless steel hardware. The racking was mounted on stainless steel strut on aluminum standoffs. PV bonding was performed per industry standards at the time by looping #10 bare copper wire around provided screws using provided cup washers to prevent the copper from contacting the aluminum frame of the modules. See photos below for the general concept of this install.

racking
Direct Power racking on stainless strut, ready for modules. Completed original install. Note proximity of ocean. SolarWorld PV on DPW racking on stainless strut.

2010: The home was remodeled and expanded. We were contracted to remove rows of modules to allow for construction. When we did so, we found considerable corrosion. The module frames at grounding points and attachment points were disintegrating. See below.

ground screw mounting holes
Ground screw in 2010. Note use of stainless cup washer to prevent contact between copper and aluminum frame, as prescribed. Module mounting hole. This is where provided stainless bolt was used to attach frame to DPW racking at factory provided mounting holes.

2010 Repair: After meeting with Solar World, a plan was established to reinstall the damaged modules. Direct Power brand Power Rail would be anodized and then bolted to the existing racking strong-backs. The PV modules would be attached using standard rail clips. Bonding would be reestablished using Solar World provided lugs. At this time the system was expanded to include 17 new Solar World modules with Enphase M190 inverters.

rail on angle rail on angle complete
Direct Power Power Rail bolted to existing strong-backs. One row completed, one more to change. Detail of attachment of Power Rail to strong back. We also removed all of the non-stainless strut nuts and replaced them with stainless.

2015 Repairs: Several of the Enphase inverters failed. When we responded we discovered that corrosion had again occurred, causing significant damage, mostly to module frames. Specifically, the locations on the module frames where the bonding lugs attached had corroded to the point where the frames disintegrated at the touch. The module frames also degraded where the stainless rail-clamps contacted them resulting in holes in the frames. See photos below.

bonding failure frame_failure_at_clip
The module frames corroded significantly at the bonding lug attachment points, to the extent that the frames failed when the bonding wires were moved slightly. The module frames also corroded where the stainless mounting clips contacted them. Note also that the extruded slot in the rail is failing. This and the module frame failures portend a structural failure should a wind gust exert force on the module, a likely occurrence. The module could leave the roof and cause injury or property damage.
bonding_failure_top_view_small enphase_bonding_corrosion
Another view of the failure pattern at the module bonding point. The Enphase inverters suffered also, experiencing damaging corrosion at the bonding points.

Summary: In 2006 the original system was installed and bonded using manufacturer's provided hardware and following manufacturer's instructions. Four years later the system was observed to have significant corrosion. The existing system was reinstalled and new equipment installed in 2010 at the direction of the module manufacturer. Five years later the corrosion problems are back. These problems will cause premature failure of the entire PV system and could lead to risk to safety of life and property. We are looking for advice from the manufacturers and the industry at large on how to remedy this problem.