RV & Camper Gear: 316 vs 201 Stainless Steel Sinks and Fixtures

An RV sink is not the same application as a residential kitchen sink. It is mounted in a small, mobile space where condensation is constant, water is often hard, and the exterior of the vehicle - including trim and fittings - is regularly exposed to road salt splash in winter. Under these conditions, the choice between grade 316 (UNS S31600) and grade 201 (UNS S20100) stainless steel has a direct effect on how long a sink or fixture stays free of pitting and staining. This article explains the material difference quantitatively and translates it into practical selection and maintenance rules.

1. Chemical Composition: 316 vs 201

Element (wt%)	316 (UNS S31600, ASTM A240)	201 (UNS S20100, ASTM A240)
Carbon, max	0.08	0.15
Manganese	2.00 max	5.50–7.50
Silicon, max	0.75	1.00
Phosphorus, max	0.045	0.060
Sulfur, max	0.030	0.030
Chromium	16.0–18.0	16.0–18.0
Nickel	10.0–14.0	3.50–5.50
Molybdenum	2.00–3.00	-
Nitrogen	0.10 max	0.25 max

The decisive difference is molybdenum: 316 carries 2.0–3.0 % Mo, while 201 contains none. In the 200-series design, manganese (5.5–7.5 %) partly replaces nickel to lower cost. Molybdenum is the element that most strongly resists chloride-induced pitting, which is exactly the failure mode an RV sink faces.

2. Pitting Resistance: The PREN Comparison

Chloride pitting resistance is quantified by the pitting resistance equivalent number, calculated as PREN = %Cr + 3.3 × %Mo + 16 × %N:

316: PREN ≈ 16–18 (Cr) + 3.3 × 2.0–3.0 (Mo) + 16 × 0.05–0.10 (N) ≈ 23–27.

201: PREN ≈ 16–18 (Cr) + 0 (Mo) + 16 × 0.15–0.25 (N) ≈ 18–22, with no molybdenum contribution.

Road salt is a mixture of sodium chloride, calcium chloride and magnesium chloride - all strong pitting promoters. Hard water leaves calcium carbonate scale that traps chlorides against the metal surface, creating a classic crevice-corrosion cell under every deposit. The higher PREN of 316 means the passive film survives far longer in this combination of chloride plus crevice conditions.

3. Grade Selection by Component Function

Sink bowls, faucets and wetted surfaces - 316

The sink bowl is wet, scratched and exposed to food acids, detergent and hard water. For this component, 316 is the engineering-reliable choice: its pitting and crevice resistance matches the real service environment, and the small cost difference is amortised over the life of the vehicle. Grade 316L (UNS S31603) adds a low-carbon limit for welded fabrications.

Cabinet handles, towel bars, exterior trim - 201 acceptable with limits

Dry-interior hardware in 201 can perform acceptably if it is kept clean and dry. The practical rules are: wipe condensation and hand-sanitizer residue promptly, avoid abrasive chloride cleaners, and replace fittings at the first sign of pitting. Exterior trim is the risk area - coastal or winter road-salt exposure will pit 201, so specify 316 for any component that faces the outside of the vehicle.

What about 304?

304 (UNS S30400) sits between the two: PREN ≈ 18–20, better than 201 but clearly below 316. For an RV sink, 304 is a reasonable minimum for dry-country use; 316 is the safe specification where road salt or coastal air is part of the operating envelope.

4. Cleaning and Maintenance That Protects the Surface

Hard-water deposits: soak paper towels in white vinegar, lay them on the deposits for about 1 hour, rinse and buff dry. Repeat monthly where water is hard.

Scratches and light discolouration: rub gently with a baking-soda paste working along the grain direction, then rinse. Deep scratches on 316 can be professionally re-finished; scratches on 201 expose a lower-alloy surface and re-finishing gives less benefit.

Avoid: hydrochloric-acid descalers, bleach-based cleansers left in contact, steel wool that embeds carbon steel particles, and leaving salt water to dry on the surface.

Exterior trim: apply an automotive wax or polymer sealant quarterly, and check seams and edges for salt accumulation after coastal or winter trips.

Ventilation: keep the sink area ventilated - reducing condensation is the cheapest corrosion prevention available.

5. Common Misconceptions

"201 is stainless, so it cannot rust." All stainless steels can pit; 201 simply pits much sooner under chloride exposure because it has no molybdenum.

"316 and 304 are the same in an RV." In hard-water or salt environments, the molybdenum in 316 is precisely the difference between a 10-year sink and a 2-year sink.

"Polishing makes a sink more corrosion resistant." A smooth, clean surface helps, but polishing cannot add molybdenum. Grade, not gloss, determines chloride resistance.

Frequently Asked Questions

Why is 316 recommended for RV sinks instead of 201?

Because the RV environment - road salt, hard water, condensation - is chloride-rich. The 2.0–3.0 % molybdenum in 316 raises its PREN to about 23–27, giving far better resistance to pitting and crevice corrosion than 201, which contains no molybdenum.

Can 201 be used anywhere in an RV?

Yes, for dry interior hardware such as cabinet handles and trim, provided condensation and sanitizer residue are wiped away promptly and the part is replaced at the first sign of pitting. Keep 201 away from sinks, exterior fittings and coastal use.

How do I remove hard-water buildup without damaging the sink?

Soak paper towels in white vinegar and lay them on the stains for about an hour, then rinse and buff dry. Repeat monthly. Avoid abrasive scouring pads and acid descalers, which attack the passive film.

Is 201 stainless steel safe for food contact?

200-series grades are used in some food-service equipment, but for a sink that sees acidic food residues and aggressive cleaning, 304 or 316 is the safer specification. Food-contact suitability also depends on surface finish and the specific regulatory framework.

How much more does 316 cost than 201 or 304?

As a market rule of thumb, 316 sheet costs roughly 20–30 % more than 304, and 201 is typically cheaper than 304. For a sink, the absolute price difference is small compared with the cost of replacement and interior damage from a corroded unit.

What is the best grade for an RV exterior fixture?

Use 316 (or 316L for welded parts). Exterior trim faces direct road-salt and UV exposure; 201 will pit quickly, and even 304 is marginal in coastal winter conditions.