Are these junction boxes suitable for domestic lighting?
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Ground connection via clamping to the DIN rail is industry standard since many decades, but the rail and clamp ratings must be considered.
DIN rail corrosion is only a problem in aggressive environments like salt water, chemical industry etc., if the box has a low IP code. The plated rails normally do not corrode even after half a century. Furthermore, a closed junction box does have a slightly higher temperature thus lowering the possibility for corrosion.
There are special types of DIN rails made of aluminum or copper to ensure low resistance. In some countries a normal steel DIN rail must not be used for the PEN, but can be used as pure PE.