Hello to everyone.I want to ask what causes starters to blacken and why it happens ? Can this be prevented in manufacturing and why starters fail after long service life ?

Fluorescent starters, are actually glow lamps with a tube filled with gas and two bi-metallic electrodes. The glow discharge that appears around them, causing them to sputter, and this is what causes the blackening. This is common with all glow lamps, and not limited to starters.

Fluorescent starters, are actually glow lamps with a tube filled with gas and two bi-metallic electrodes. The glow discharge that appears around them, causing them to sputter, and this is what causes the blackening. This is common with all glow lamps, and not limited to starters.

Thanks for reply.So gas sticks on glass and with arcing it makes it black ?

No. The bi-metal contacts sputters with time, when the glow discharge appears around them.

But unlike the glow lamps (those intended to produce light), the starters can tolerate quite heavy sputtering, so usually that is not their life limitting problem (internally the discharge does not care if its light can escape or not).

What is mimitting their life is usually fatigue of the bimetalic strip itself (the welding, as well as the material alone; there are quite large stresses within the strip; it tend to delaminate or crack), of the welds holding it in place (the stripe falls off) mainly the contact area being disturbed so much it welds permanently.
Second problem use to be the heat deterioration of the surrounding components: The capacitor, the case and socket contact connections.
All of that tends to proggress way faster if the starter is hot as whole, as well as with the number of starter switching cycles (it usually does few cycles per lamp start, but once the lamp fails, it is forced to make 1000's of cycles within each hour).

Starters where the weld fails are very bad starters - The glow lamp will keep glowing continuously, this makes the starter case melt, destroy the starter socket in the luminaire and sometimes catch fire

Starters where the weld fails are very bad starters - The glow lamp will keep glowing continuously, this makes the starter case melt, destroy the starter socket in the luminaire and sometimes catch fire

I have seen that on some ballasts that stuck starter burned them.Crappy starters (Fake Philips)usually cause this.

Fake Philips with the bad weld fault https://www.lighting-gallery.net/gallery/displayimage.php?album=2032&pos=4&pid=107895