Acetic acid release

Acetic acid forms when the EVA encapsulant breaks down. Heat and water drive this by hydrolysis, and UV light may speed it up. Glass and backsheet seal in the EVA, so the acid cannot easily escape. It can build up in front of the cells and lower the local pH. The acid corrodes cell gridlines, solder bonds and the copper and tin of the interconnect ribbons. Series resistance rises and module power falls, which is severe metallization corrosion. Corroded solder bonds can show green copper acetate patterns. Copper exposed to the EVA can turn it brown. Acetic acid also makes potential induced degradation worse because it helps sodium ions move from the glass to the cells. It can also promote delamination and speeds up the oxidation of the EVA itself. Corrosion is worse when moisture gets in, for example near delamination, at cell edges or behind broken glass. It is also worse in hot, humid, farming or coastal locations. To reduce exposure, choose encapsulants without acetic acid, such as polyolefins, or backsheets that let the acid escape. Also check the IEC 61215 certificate and the bill of materials, and inspect the system regularly.

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• sentence 3: support check: partial - Passages support corrosion of gridlines, solder bonds, Cu/Sn ribbons and the rise in series resistance and power loss, but nothing defines this as 'severe' metallization corrosion (u6 only notes advanced corrosion can drop power below 80%). -->