Freeman Marine Stainless Steel Deck Rings & Coamings (2400 Series)

Technical Guide: Welding and Properties of Stainless Freeman Coamings

Freeman marine-grade stainless steel deck rings (AISI 316L / EN 1.4404) are engineered for vessels and architectural applications where carbon steel or marine aluminum cannot meet chemical or aesthetic criteria. Welded directly into stainless deck plating, they deliver superior resistance against acids, harsh chemicals, salt-laden atmospheres, and pitting corrosion.

1. Welding Procedures and Heat Input Control

• Precision Deck Cutouts: Machine or cut the deck cutout to tight tolerances against the coaming perimeter to minimize joint root gaps. Excessive gap buildup requires heavy filler metal, increasing localized heat input and thermal distortion risks in austenitic stainless steel.
• Cross-Staggered Tack Welding: Apply short tack welds in a cross-staggered sequence on opposite sides (180 degrees). Allow joints to cool between tacks.
• Low-Heat Welding Techniques (TIG / Pulsed MIG): Complete full-penetration welding using short, balanced passes and controlled amperage to preserve the metallurgy and prevent chromium carbide precipitation (sensitization).
• Rigid Fixturing: Keep the hatch cover dogged in place or clamp a rigid strongback fixture across the coaming during welding and cooldown to ensure the sealing plane remains perfectly flat.
• Pickling and Passivation: After final welding, all weld seams and heat-affected zones must be thoroughly pickled and passivated to restore the stainless steel's protective passive oxide layer.

2. Sealing Profiles: Compression vs. Knife-Edge

• Stainless Rings for Compression Seals: Feature a raised solid spigot without an outer collection gutter. Requires zero drain plumbing and is the proven choice for decks where easy washdown and flush transit are prioritized.
• Stainless Rings for Knife-Edge Seals: Feature a machined knife-edge rim flanked by an integrated perimeter drainage gutter. The gutter captures deck runoff, allowing the boatyard to install a drain fitting in the gutter base if desired to discharge standing water before the hatch is opened in heavy weather.

3. Hinged Geometry and Open Resting Position

On hinged models (suffix -H or -HK), the stainless steel coaming is supplied with heavy-duty integrated hinge lugs. Freeman's marine hinge mechanism allows the cover to open past 180 degrees, resting flat and securely against the deck plating. This eliminates mechanical leverage on hinge pins and prevents gusting winds or heavy seas from slamming the hatch shut.