Severe metallization corrosion is the chemical attack of a cell's busbars and interconnect ribbons after water and oxygen get into the module. Heat and moisture break down the encapsulant, usually EVA, which releases acetic acid that corrodes the metal. Delamination, a poor backsheet, broken glass and PID can all speed this up. Some corrosion is normal over a module's life, but advanced corrosion can sharply cut module power. Damp-heat tests found losses of up to 80% in the worst case. Corrosion is usually easy to spot visually. Electroluminescence images also show it. On an IV curve it shows as a lower fill factor from higher series resistance, along with a lower short-circuit current. Thermography also helps confirm the electrical impact. Because corrosion is often uneven, it can cause mismatch and hotspots, overwork bypass diodes and weaken cell interconnections. Replace severely corroded modules, find out where the water is getting in, and choose module designs and installation practices that limit moisture exposure.
<!-- review notes
caused_byc1 drafted · lead Moisture exposure
Water and oxygen getting into the module start the corrosion process.
sec=front h=05a21582ed7bsec=h2 h=f411297a4a32sec=h3 h=924544636200sec=h4 h=de0a5bfe7306c2 drafted · lead Acetic acid release
Acetic acid forms when the encapsulant, usually EVA, hydrolyses in the presence of heat and water.
sec=h6 h=ab4b4f0e5fd4sec=h4 h=de0a5bfe7306c3 drafted · lead High operating temperature
Heat drives encapsulant hydrolysis. How sensitive the encapsulant is to heat is a key factor.
sec=h4 h=de0a5bfe7306c4 drafted · lead UV exposure
UV stress was considered a possible factor that helps acetic acid form.
sec=h4 h=de0a5bfe7306c5 drafted · lead Delamination
Delamination lets water move into the module layers and often sets off encapsulant degradation.
sec=h6 h=ab4b4f0e5fd4sec=h4 h=de0a5bfe7306c6 verified · fact Discoloration
Degraded encapsulant shows yellowing before it promotes corrosion through acetic acid release.
sec=h6 h=ab4b4f0e5fd4verified by: joshuahamsaverified on: 2026-10-16
c7 drafted · lead Glass Breakage
Broken glass lets water in and speeds up corrosion.
sec=h6 h=ab4b4f0e5fd4c8 drafted · lead Potential Induced Degradation (PID)
PID can raise corrosion levels through its own mechanisms.
sec=h6 h=ab4b4f0e5fd4affectsc9 drafted · lead Solar cell
The corrosion attacks the cell busbars and metal grid.
sec=h4 h=de0a5bfe7306c10 drafted · lead Cell interconnect ribbon
Ribbons are attacked, and corrosion weakens the cell interconnections.
sec=h6 h=ab4b4f0e5fd4sec=h4 h=de0a5bfe7306presents_asc11 drafted · lead Increased series resistance
sec=h7 h=7c7e8aa5f488sec=front h=05a21582ed7bsec=h2 h=f411297a4a32c12 verified · fact Reduced fill factor
sec=h7 h=7c7e8aa5f488verified by: joshuahamsaverified on: 2026-10-16
c13 drafted · lead Reduced short-circuit current
sec=h7 h=7c7e8aa5f488c14 verified · fact Visible corrosion marks
Corrosion is easy to see during visual inspection.
sec=h7 h=7c7e8aa5f488sec=front h=05a21582ed7bsec=h2 h=f411297a4a32verified by: joshuahamsaverified on: 2026-10-16
detected_byc15 drafted · lead Visual inspection
Look for corrosion and damage to the encapsulation.
sec=h7 h=7c7e8aa5f488sec=front h=05a21582ed7bsec=h2 h=f411297a4a32c16 drafted · lead Electroluminescence imaging
sec=h7 h=7c7e8aa5f488sec=front h=05a21582ed7bsec=h2 h=f411297a4a32c17 drafted · lead IV curve tracing
The IV curve shows a lower fill factor because series resistance rises, plus a lower Isc.
sec=h7 h=7c7e8aa5f488sec=front h=05a21582ed7bsec=h2 h=f411297a4a32c18 verified · fact Infrared thermography
sec=front h=05a21582ed7bsec=h2 h=f411297a4a32verified by: joshuahamsaverified on: 2026-10-16
leads_toc19 drafted · lead Module Hotspot from Cell Damage
Corrosion is often uneven across the module, which creates mismatch and possible hotspots.
sec=h6 h=ab4b4f0e5fd4c20 verified · fact Bypass Diode Failure
Mismatch can switch on bypass diodes, and running longer than intended speeds up their ageing.
sec=h6 h=ab4b4f0e5fd4verified by: joshuahamsaverified on: 2026-10-16
c21 verified · fact Cell Interconnection Failure
Weakened interconnections can fail from fatigue, with brown marks.
sec=h6 h=ab4b4f0e5fd4verified by: joshuahamsaverified on: 2026-10-16
mitigated_byc22 drafted · lead Module replacement
Applies to severely corroded modules.
sec=front h=05a21582ed7bsec=h2 h=f411297a4a32c23 drafted · lead Root cause investigation
Find out why water is getting in.
sec=front h=05a21582ed7bsec=h2 h=f411297a4a32c24 verified · fact Moisture-resistant module design
Favour module designs that limit moisture exposure.
sec=front h=05a21582ed7bsec=h2 h=f411297a4a32verified by: joshuahamsaverified on: 2026-10-16
c25 drafted · lead Proper installation
Favour installation practices that limit moisture exposure.
sec=front h=05a21582ed7bsec=h2 h=f411297a4a32typical_power_lossc26 drafted · lead ≤ 80 PERCENT
Conditions: Worst-case drop in module maximum power from corrosion caused by water ingress, seen in damp-heat tests
sec=h3 h=924544636200review note: support check: partial - 80% is stated as a worst-case drop in damp-heat tests, not a typical value.
related_to c4leads_to c8leads_to c20caused_by c9leads_to c24leads_to c15leads_to c23