Desalination Maintenance: Corrosion-Resistant Nylon Valves and Pump Components

Keeping a seawater reverse osmosis (SWRO) plant online is a battle against chloride stress, biofouling, and supply-chain delays for critical spares. This is where Selective Laser Sintering (SLS) PA12 (nylon 12) shines. It’s lightweight, tough, resists saltwater corrosion, and can be printed in days—perfect for custom valve internals, pump wear parts, housings, guards, and adapters that keep you running between major shutdowns. Evonik’s PA12 family is well known for low water uptake and resistance to oils, fuels, and salt solutions—properties that translate directly to desalination duty cycles. ([Vestamid][1])

Below is a practical guide for U.S. maintenance engineers and reliability teams on selecting SLS PA12, designing seals that actually hold, and choosing finishes that extend service life inside chlorination/dechlorination environments.

Why SLS PA12 belongs in your plant

Corrosion resistance in seawater. Sintered PA12 parts (e.g., EOS PA2200) show strong performance in saline environments—“Sea Water: + +”—and cold-saturated sodium chloride per the material’s chemical resistance tables. Mechanical properties for printed parts typically include ~45 MPa tensile strength, ~20% elongation, and Shore D ≈ 75; water absorption is ~0.52% at 23 °C/50% RH and ~1.93% at saturation (DIN 53495), supporting dimensional stability in humid service.

Dimensional accuracy & fast turns. SLS commonly holds ±0.3% (≥±0.3 mm) with minimum wall thickness from ~0.8–1.0 mm, enabling reliable press-fits and seal features without tooling. For tighter interfaces, design locally for post-machining. ([materialise.com][2], [protolabs.com][3], [Xometry Pro][4])

Made-to-fit spares. Because there’s no mold, you can mirror worn legacy geometries and integrate features (O-ring glands, thread-insert bosses, keyways) directly into the print, cutting change-out time on skids and in cramped MCC rooms.

Mapping the environment: what your parts will actually see

Chlorination & dechlorination reality. Most SWRO intakes dose oxidants for bio-control (e.g., 0.5–1.0 mg/L free chlorine). Just before RO, plants must dechlorinate (e.g., sodium bisulfite) because polyamide RO membranes are chlorine-sensitive. Understanding this chemistry helps you decide where nylon parts can live and when you should shield them. ([dupont.com][5], [PMC][6])

Hypochlorite contact. PA12 handles seawater and brine very well. With sodium hypochlorite, compatibility depends on concentration and temperature: EOS data show 5% NaOCl is “practically resistant” at 20 °C but not resistant at 60 °C—typical of oxidizers with polyamides. In practice: avoid continuous contact with strong or hot bleach; isolate with elastomer seals or move PA12 out of the wetted path in chlorination loops.

Quick rule: PA12 is excellent for saltwater and many coagulants, but design respectfully around oxidizers. For high-chlorine CIP lines or hot hypochlorite tanks, use metals rated for NaOCl or fluoropolymers and keep nylon out of the wetted zone. Industry materials references echo the aggressiveness of hypochlorite on many materials. ([bssa.org.uk][7])

Where SLS PA12 works best in desalination

  • Valve internals: cages, spacers, pilot housings, actuator covers, positioner brackets, position indicator caps—non-wetted or partially wetted parts away from hot oxidizers.
  • Pump components: wear rings, diffuser or volute inserts, seal-retainer plates, cable/strain-relief glands, protective guards. Limit high-speed impellers to low head/low temperature applications and verify with a short field trial.
  • Dosing skids & pretreatment: custom manifolds, sensor holders, splash-guards, peristaltic pump adapter plates, strainer accessories, and sight-glass shields.

Nickel Institute guidance on desalination materials highlights how chloride stress and galvanic couples drive failure modes—lightweight polymer components can remove those corrosion pathways entirely where loads allow. ([nickelinstitute.org][8])

Property snapshot for SLS PA12 (what you can count on)

Property (EOS PA2200) Typical Value
Density 0.90–0.95 g/cm³
Tensile strength ~45 MPa
Elongation at break ~20%
Shore D hardness ~75
Vicat softening 163–181 °C
Service temp (steady) ~-40 to +80 °C (short-term up to 160 °C without load)
Water absorption ~0.52% (23 °C/50% RH) / ~1.93% saturated

Data summarized from EOS PA2200 material documents.

Sealing strategies that work (and why they fail)

Even great material selection loses to a leaky interface. Build your sealing plan at the CAD stage:

  1. O-ring glands to AS568: Use standard dash sizes and Parker’s design charts for squeeze, stretch, and groove fill. Keep generous lead-ins and avoid knife-edge landings that nick elastomers. ([Parker Hannifin Corporation][9])
  2. Compression limiters: For bolted covers and flanges, add metal compression limiters so clamp loads don’t creep the polymer; you’ll maintain gasket stress across thermal cycles. ([Aerotecnica][10])
  3. Threaded inserts: Heat-stake or ultrasonic brass/aluminum inserts into printed bosses for durable threads—design the pilot hole per insert spec to ensure full plastic flow and pull-out strength. ([spirol.com][11], [PEM][12])
  4. Elastomer choice: In chlorinated seawater, EPDM is common; match elastomer to your chemistry and temperature per the seal vendor’s tables. (See Parker ORD-5700 guidance.) ([Parker Hannifin Corporation][9])

Make it hold pressure: print design notes for SLS PA12

  • Tolerances: Assume ±0.3% (≥±0.3 mm); datum critical faces can be skim-cut after printing if you need better. ([materialise.com][2], [Xometry Pro][4])
  • Wall thickness: Start at 2.5–3.0 mm for pressure-bearing shells (above generic 0.8–1.0 mm minimums) and rib for stiffness instead of just adding mass. ([Protolabs Network][13])
  • Holes & channels: Keep ≥1.5 mm diameter to evacuate powder; add cleanout ports on dead-legs. ([Protolabs Network][13])
  • Flat gaskets: If you must use them, include a 0.2–0.3 mm step to contain squeeze and reduce creep.
  • Post-machining: Leave 0.3–0.5 mm stock on sealing faces you plan to machine.
  • Traceability: Emboss part and revision (≥0.8 mm stroke, ≥0.8 mm depth/height) for in-plant kitting. ([materialise.com][14])

Finishes that boost longevity (especially around chlorine)

  • Vapor smoothing (chemical polishing): Seals surface porosity, improves water/air tightness, and reduces biofilm adhesion—ideal for housings, covers, and wetted features you want to clean easily. Multiple vendors document sealed, water-repellent surfaces after smoothing. ([AMT PostPro][15], [dyemansion.com][16])
  • When chlorine is nearby: Keep smoothed PA12 out of continuous contact with hot or concentrated hypochlorite; use seals and design for splash/spray zones instead of immersion. (See the compatibility note above.)

Where nylon fits into chlorination workflows

  • Upstream intake & pretreatment: Many systems chlorinate to 0.5–1.0 mg/L free chlorine for bio-control and then dechlorinate (e.g., SBS) before the RO membranes. Nylon components can live safely in housings, guards, valve actuators, and non-wetted features here—as long as you shield them from hot/strong hypochlorite and position them out of direct immersion. ([dupont.com][5])
  • RO trains: Since RO membranes are chlorine-sensitive, anything plastic near the trains typically sees low oxidant exposure—good news for PA12 fixtures and covers. ([dupont.com][17])

What to order for fast wins (typical part list)

  • Valve: pilot housings, bonnet covers, indicator caps, handwheel adapters, positioner brackets.
  • Pump: wear rings, spacer sleeves, wire-guard/strain reliefs, drip-trays, shrouds, sensor mounts.
  • Skids: manifold clamps, filter key tools, probe holders, cable-routing organizers, custom guards.

Implementation checklist (5 steps to first parts)

  1. Upload CAD for a nylon 3d printing service quote; specify SLS PA12 and your operating conditions (temp, chemistry, pressure).
  2. Pick sealing: AS568 O-ring size + elastomer, compression limiters, and any flat gaskets. ([Parker Hannifin Corporation][9], [Aerotecnica][10])
  3. Add inserts: Call out heat-stake inserts (thread, length) and boss pilot diameter/depth per the insert datasheet. ([spirol.com][11])
  4. Choose finish: Vapor smoothing for sealed, cleanable surfaces; dye or coat for UV exposure. ([dyemansion.com][16])
  5. Approve test lot: Install in non-critical service first, log inspection intervals, and release to broader use.

FAQs

Will SLS PA12 hold up in seawater?

Yes. Material data show seawater and saturated NaCl compatibility, with low water uptake supporting dimensional stability.

What about bleach (sodium hypochlorite)?

At 5% NaOCl, PA12 is practically resistant at ~20 °C but not resistant at 60 °C. For continuous/hot hypochlorite, isolate nylon with seals or keep it out of the wetted path.

Are SLS parts watertight?

Raw SLS surfaces are micro-porous; vapor smoothing significantly improves liquid-tightness and cleanability. Choose adequate wall thickness and consider post-machining of sealing lands. ([AMT PostPro][15], [Formlabs][18])

What tolerances can I expect?

Plan for ±0.3% (≥±0.3 mm) as-printed; machine critical faces if needed. ([materialise.com][2], [Xometry Pro][4])

Any RO-specific cautions?

RO membranes are not chlorine-tolerant; plants chlorinate upstream and dechlorinate just before the membranes. That means many nylon parts near the trains see low oxidant exposure—good placement for PA12 components. ([dupont.com][17])

Ready to print?

We specialize in industrial 3D printing for water treatment, with SLS nylon 3D printing tuned for desalination maintenance: rapid turnaround spare parts, corrosion resistant nylon parts, and custom nylon valve replacement kits. Upload your CAD and note “nylon 3d printing service for desalination” in the RFQ—our applications team will set you up with the right sealing strategy and finishing plan.

References & technical links