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What Is Electrolyte Use In Electrolytic Capacitor

By on August 27, 2008


Ever wander what is the type of oil leaked from the electrolyte capacitor? After few years in service some cheap electrolytic capacitor begin to bulge and some have the electrolyte leaked from bottom and this electrolyte could destroy the corresponding circuit or components. Even in some branded electrolytic capacitor that have a rating of 105 degree celcius could also give problem especially in the environment that have less or no ventilation in many older HP laser jet printers. The power supply of the HP laser jet was totally covered and these e-caps problem were mainly electrolyte leaked . Many times, replacing and cleaning the power board after repair solved the no power problem in laser jet switch mode power supplies.

Here is a definition of electrolyte:

The electrolyte is usually boric acid or sodium borate in aqueous solution together with various sugars or ethylene glycol which are added to retard evaporation. Getting a suitable balance between chemical stability and low internal electrical resistance is very tricky and in fact, the exact composition of high-performance electrolyte is a closely guarded trade secret. It took many years of painstaking research before reliable devices were developed.

Electrolytes may be toxic or corrosive. Working with the electrolyte requires safe working practice and appropriate protective equipment such as gloves and safety glasses. Some very old tantalum electrolytics, often called “Wet-slug”, contain corrosive sulfuric acid, however most of these are no longer in service due to corrosion.

Source from Wikipedia



  1. Steele Braden

    October 5, 2012 at 7:34 pm

    Dear Sir, I am wanting to make up some experimental electrolytic capacitors.
    The aluminium foils will be immersed in liquid electrolyte in a jar.
    Can you tell me the concentration of sodium borate in the water solution?
    Is there an optimum current per square inch to be used when forming the anode which should not be exceeded?
    I see that some commercial electrolytics are available up to 600 volt rating.
    I wish to obtain a working voltage of 200 to 300 volts.
    What forming voltage is required?
    The leakage current through commercial capacitors - 5 microamps at 12 volts on a 1,000uf 35 volt cap.
    Can I expect similarly low leakage current?
    Thankyou in advance.
    Steele Braden.

    • Jestine Yong

      October 5, 2012 at 11:13 pm

      Hi Steela,
      I guess I could not help you on this matter because my profession is in electronics repair and not in doing experimental work on electronics components.I suggest that you visit forum that is related to this subject. If you have any electronics repair question you can always email me.



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