What is the difference between spot welding and arc welding?

There are lot of differences between spot and arc welding.

1. Arc welding belongs to Fusion welding (Liquid state welding), whereas Spot welding technically termed as Resistance spot welding is a solid state joining process.  https://disqus.com/by/brentbosse/
2. In arc welding, the base metals are melted by means of an electric arc produced by maintaining a small distance between the electrode and the base metals. But in spot welding, electric current is made to pass through the base metals and they get welded due to heat produced from the resistance developed.  https://www.openstreetmap.org/user/Christopher%20L%20Johnson
3. Arc welding uses consumable or non consumable electrode depending on the application. Spot welding uses an electrode and a ground to pass the current, both of them being non consumable.

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4. Arc welding may or may not require filler metal. In spot welding, there is no need for filler metal.  

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5. Because of the flux used in arc welding, slag is formed on the weld bead which has to be removed while finishing operations. There is no slag formation in spot welding.

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7. Base metals of various sizes can be joined using arc welding. Spot welding can be used only for welding sheet metals having thicknesses less or nearly 3mm. 

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8. Joining of metals using arc welding is a time consuming process. Resistance spot welding can be done within minutes. 

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9. Higher level of skills are required for arc welding. Spot welding comparatively demands less skills. 

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