Editing Fluorescent lamp (section)

===End of life===
The life expectancy of a fluorescent lamp is primarily limited by the life of the cathode electrodes. To sustain an adequate current level, the electrodes are coated with an emission mixture of metal oxides.  Every time the lamp is started, and during operation, a small amount of the cathode coating is [[sputtering|sputtered]] off the electrodes by the impact of electrons and heavy ions within the tube. The sputtered material collects on the walls of the tube, darkening it. The starting method and frequency affect cathode sputtering.  A filament may also break, disabling the lamp. 
[[File:Fluorescent wear - sputter.png|thumb|right|This tube failed after it had been turned on many times. Too much of the thermionic emission mix had sputtered off the cathodes, sticking to and blackening the glass.]]
[[Image:Thermionic filament.jpg|thumb|left|The filament of a low-pressure mercury gas-discharge lamp, with white [[thermionic emission]] coating acting as [[hot cathode]]. A little of the coating is [[Sputtering|sputtered away]] at every start; the lamp ultimately fails.]]

Low-mercury designs of lamps may fail when mercury is absorbed by the glass tube, phosphor, and internal components, and is no longer available to vaporize in the fill gas. Loss of mercury initially causes an extended warm-up time to full light output, and finally causes the lamp to glow a dim pink when the argon gas takes over as the primary discharge.<ref>{{cite conference |last1=Corazza |first1=A. |last2=Giorgi |first2=S. |last3=Massaro |first3=V. |title= Mercury Dosing in Fluorescent Lamps |book-title=2008 IEEE Industry Applications Society Annual Meeting |pages=1–4 |conference=Industry Applications Society Annual Meeting |date=5–9 October 2008 |issn=0197-2618 |publisher=IEEE |doi= 10.1109/08IAS.2008.237}}</ref>

Subjecting the tube to asymmetric current flow, effectively operates it under a DC bias, and causes asymmetric distribution of mercury ions along the tube. The localized depletion of mercury vapor pressure manifests itself as pink luminescence of the base gas in the vicinity of one of the electrodes, and the operating lifetime of the lamp may be dramatically shortened. This can be an issue with some poorly designed [[inverter (electrical)|inverters]].<ref>{{cite web|url=http://www.htl.co.jp/img/p_pro4_p10.pdf|archive-url=https://web.archive.org/web/20071022003220/http://www.htl.co.jp/img/p_pro4_p10.pdf|url-status=dead|archive-date=22 October 2007|title=Cold Cathode Fluorescent Lamp|publisher=Harison Toshiba Corp.|access-date=22 October 2007}}</ref>

The phosphors lining the lamp degrade with time as well, until a lamp no longer produces an acceptable fraction of its initial light output.

Failure of the integral electronic ballast of a compact fluorescent bulb will also end its usable life.

[[File:Mercury Adsorbed CFL.jpg|thumb|right|Compact fluorescent lamp that has reached end of life because of mercury [[adsorption]]. Light is produced only by the base argon fill.]]