Quick Hits

EPISODE 7 — Corrosion & Deterioration Protection (300.8)

Slide 1 — Hook "How raceways, boxes, and fittings get protected from rusting out or breaking down in harsh environments."

Slide 2 — 300.8(A) Ferrous metal equipment

• Ferrous (iron-containing) raceways/boxes/cabinets/fittings/hardware need corrosion-resistant coating inside AND out — stainless steel is exempt. Field-cut threads need an approved conductive, corrosion-resistant compound.

• Enamel-only protected equipment can't go outdoors or in wet locations.

• Boxes/cabinets with approved organic coatings marked "Raintight," "Rainproof," or "Outdoor Type" ARE allowed outdoors.

• Ferrous equipment in concrete, direct earth contact, or severely corrosive areas needs materials/protection approved specifically for that condition.

Slide 3 — 300.8(B), (C), (D)

• (B) Aluminum equipment embedded/encased in concrete or in direct earth contact needs SUPPLEMENTARY corrosion protection.

• (C) Nonmetallic equipment must be approved for the condition — sunlight-exposed materials need to be listed/identified as sunlight resistant; chemical-exposed materials need to be inherently chemical-resistant or specifically identified for that chemical.

• (D) Indoor wet locations (dairy facilities, laundries, canneries, frequently washed walls, damp absorbent surfaces): exposed wiring systems need at least ¼" airspace from the wall/supporting surface — EXCEPT nonmetallic raceways/boxes/fittings on concrete/masonry/tile can skip the airspace.

Slide 4 — Quiz + CTA Q: "In an indoor wet location like a dairy processing facility, exposed metallic wiring systems generally need what minimum airspace from the wall?" A) 1/8 in. B) 1/4 in. C) 1/2 in. D) 1 in.

✅ Answer: B — 300.8(D): at least ¼" (6 mm) airspace.

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