CSLB C-10 Electrical ContractorWiring Methods and MaterialsMedium
A rigid metal conduit (RMC) run will be installed underground and encased in concrete that is in direct contact with corrosive soil. Per NEC 344.10(B), what additional protection is required?
- AA sacrificial anode must be installed at each conduit termination
- BNo additional protection is needed since concrete encasement is sufficient
- CSupplementary corrosion protection, such as an approved coating, must be applied
- DThe conduit must be replaced with PVC conduit instead of RMC
Show answer & explanationAnswer & explanation
Correct answer: C. Supplementary corrosion protection, such as an approved coating, must be applied
NEC 344.10(B) requires that ferrous raceways such as RMC installed in concrete slabs in contact with earth in areas subject to severe corrosive influences receive supplementary corrosion protection, such as an approved coating (e.g., PVC coating) beyond the concrete encasement itself.
Why the other options are wrong
- A. Sacrificial anodes are a cathodic protection method not specified by this code section.
- B. Concrete alone does not always protect against corrosive soil conditions.
- D. RMC can still be used if properly protected; replacement is not mandated.
RMC Corrosion Protection
Ferrous metal conduit installed in contact with corrosive soil or concrete requires supplementary corrosion protection beyond standard galvanizing.
- Applies to RMC and other ferrous raceways
- Concrete encasement alone may not be enough in corrosive soils
- Approved coatings like PVC jacketing satisfy this requirement
Memory trick: Corrosive soil needs a coat, not just concrete