Author Topic: Neon lamp leads corroding  (Read 624 times)

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Offline XenonTopic starter

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Neon lamp leads corroding
« on: January 02, 2022, 11:36:43 am »
In old CRT equipment (being a monitor or scope) you often find neon lamps in the HV area.
For some reason yet unknown to me, the leads of these lamps are often heavily corroded.
The corrosion is always where the lead enters the bulb. This corrosion makes the lead very brittle, and it snaps at the lightest vibration.
Does anyone know why this happens? All other surrounding components are fine, only the neons suffer from this.
 

Offline SeanB

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Re: Neon lamp leads corroding
« Reply #1 on: January 02, 2022, 11:59:17 am »
Going to take a guess it is because the leads are made from steel wire, as glass will adhere to steel, or rather to iron oxide, quite well, so the leads are made from nice clean steel wire, and then are cleaned after manufacture with an acid dip, so that the following tin plating can be adhered to this nice clean surface. Likely there is always a residue of acid trapped in the interface area to the glass, and this gradually reacts with oxygen and water vapour in the air, to corrode the steel in the area just by the glass, eventually corroding the lead off. Neon lamps are made as cheap as possible, as they are made in the million in automated lines, so material cost is paramount, so steel wire instead of a non corroding metal, and then tin plate to enable them to be soldered or crimped with a reliable connection.

You see the same in CFL lamps, where the filament leads are steel wire, but are not coated, as they typically get wire wrapped around a post, making a gas tight connection, but use the same wire and sealing method. Neon lamps however do not run hot, which would keep the seal dry, so they will corrode with time.
 
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