Wet vs Dry Underwater Welding: Methods, Quality, Depth Limits, and Applications

Q: "Which produces better welds, wet or dry underwater welding?"

"Dry hyperbaric welding produces significantly better welds than wet welding. Inside a pressurized habitat, the welding environment is essentially the same as surface conditions (dry, controlled atmosphere, stable arc). Dry welds can meet the same quality standards as surface welds. Wet welds have inherently lower quality due to rapid quenching by surrounding water, hydrogen embrittlement from water dissociation, porosity from steam and gas generation, and limited visibility for the welder."

Q: "What electrodes are used for wet welding?"

"Wet welding uses modified E6013 or E7014 stick electrodes with waterproof flux coatings. The waterproof coating prevents the flux from absorbing water before it reaches the arc. The electrodes run on DCEN (electrode negative) polarity, which is opposite to standard surface stick welding. Some manufacturers produce specially formulated wet welding electrodes with coatings designed to displace water from the arc zone and reduce hydrogen absorption."

Q: "How deep can wet welding be performed?"

"Wet welding has been performed at depths exceeding 300 feet (91 meters), but quality and productivity decrease significantly below 100 feet (30 meters). As depth increases, ambient pressure compresses the arc, increases quench rate, and makes electrode manipulation more difficult. Most production wet welding is done at depths less than 200 feet. Below 300 feet, dry hyperbaric welding is strongly preferred for any structural application because wet weld quality degrades to the point where structural integrity can't be reliably achieved."

Published September 15, 2025 · Updated March 17, 2026 · 9 min read

Wet welding puts the diver and arc directly in the water, using waterproof stick electrodes to make welds surrounded by the ocean. Dry hyperbaric welding seals a pressurized habitat around the joint, displaces the water, and lets the welder work in a dry gas environment at ambient pressure. Wet welding is cheaper and faster to mobilize. Dry welding produces welds that actually meet structural standards. The choice depends on whether you need a temporary fix or a permanent repair.

Wet Welding Fundamentals

Wet welding is shielded metal arc welding (SMAW/stick) performed by a diver in direct contact with the surrounding water. The welding arc operates in a gas bubble created by the flux coating’s decomposition. Water immediately surrounds this gas bubble, creating a turbulent, rapidly quenching environment that fundamentally limits weld quality.

How Wet Welding Works

The diver holds a standard-format stick electrode holder (stinger) connected to a DC welding power source on the surface through a welding cable in the umbilical bundle. The power source supplies DC current, typically 150-200 amps, through the water to the work piece.

When the diver strikes an arc, the electrode coating decomposes and creates a gas bubble around the arc. Inside this bubble, the welding process is similar to surface stick welding, but the gas bubble is unstable and the surrounding water rapidly cools the weld metal and HAZ.

Wet Welding Electrodes

Standard surface welding electrodes can’t be used underwater because the flux coating absorbs water and disintegrates. Wet welding electrodes have a waterproof outer coating that protects the flux until it enters the arc zone.

Electrode Type	Application	Polarity	Notes
Modified E6013	General-purpose wet welding, mild steel	DCEN (electrode negative)	Most common wet welding electrode
Modified E7014	Higher-strength applications	DCEN	Iron powder coating, higher deposition
Modified E7018	Limited wet welding use	DCEN	Low-hydrogen intent, but water negates the benefit
Nickel-based wet rod	Cast iron repair underwater	DCEN	Specialty applications

Polarity note: Wet welding uses DCEN (electrode negative), which is the opposite of most surface stick welding (DCEP). DCEN reduces the risk of electrical shock to the diver because the electrode is at a lower potential relative to the work piece and surrounding water.

Wet Weld Characteristics

The surrounding water affects every aspect of the weld:

Rapid quenching. Water cools the weld metal and HAZ much faster than air cooling. This rapid quench produces a harder, more brittle microstructure with higher residual hydrogen content. The HAZ hardness on a wet weld can exceed 400 HV (Vickers), well above the 350 HV threshold commonly associated with hydrogen cracking susceptibility.

Hydrogen embrittlement. Water dissociates in the arc, producing hydrogen that dissolves into the weld metal. This diffusible hydrogen content is dramatically higher than surface welds (typically 30-80 mL/100g versus 5-10 mL/100g for low-hydrogen surface welding). The combination of high hydrogen and high hardness creates ideal conditions for delayed hydrogen cracking.

Porosity. Steam generation, gas bubble instability, and trapped gas produce porosity levels higher than any surface welding process. Some porosity is considered inherent to the wet welding process and is accounted for in AWS D3.6 acceptance criteria.

Reduced ductility. Wet welds consistently show lower ductility (elongation and reduction of area) than equivalent surface welds due to the harder microstructure and hydrogen content.

Property	Wet Weld (Typical)	Surface Weld (Typical)
Tensile Strength	60-70 ksi	70-80 ksi (E7018)
HAZ Hardness	300-450 HV	200-300 HV
Diffusible Hydrogen	30-80 mL/100g	5-10 mL/100g (low-hydrogen)
Porosity Level	Significant (inherent to process)	Minimal with proper technique
Elongation	5-15%	22-30%

Depth Limitations for Wet Welding

As depth increases, ambient pressure rises (approximately 0.445 psi per foot of seawater). This increasing pressure affects the welding arc and weld quality:

Arc constriction: Higher pressure compresses the arc column, making it more concentrated and harder to control
Increased quench rate: Higher pressure increases the density of the surrounding water, accelerating heat extraction
Diver performance: Nitrogen narcosis affects manual dexterity and decision-making below 100 feet on air
Electrode manipulation: The combination of current, bulky dive equipment, and restricted movement makes precise electrode control progressively harder at depth

Most production wet welding occurs at depths less than 200 feet (61 meters). The process has been performed at depths exceeding 300 feet, but quality and productivity drop off significantly below 100-150 feet.

Dry Hyperbaric Welding

Dry hyperbaric welding (also called habitat welding) takes place inside a sealed enclosure clamped around the joint at depth. Water is displaced from the habitat by pumping in breathing gas, creating a dry environment at the ambient pressure of the surrounding water.

How Dry Welding Works

A fabricated steel or aluminum habitat is lowered to the worksite and sealed around the pipe joint, structural member, or component to be welded. The water is pumped out and replaced with a breathing gas mixture (typically helium-oxygen at depth). The welder enters the habitat through a trunk or lock and welds in a dry environment.

Inside the habitat, the welding conditions are remarkably close to surface conditions:

The arc operates in a gas atmosphere, not water
The weld metal cools in gas, not water (dramatically slower quench rate)
Visibility is good (the welder can see the puddle clearly)
Standard welding processes can be used (TIG, MIG, SMAW, FCAW)

The primary difference from surface welding is that the ambient pressure inside the habitat equals the water depth pressure. At 300 feet, the habitat is pressurized to approximately 10 atmospheres. This affects gas density, arc characteristics, and the welder’s physiology (divers at this depth breathe helium-oxygen mixtures to prevent nitrogen narcosis).

Dry Welding Quality

Welds made in a properly maintained habitat achieve quality levels comparable to surface welds. The controlled atmosphere eliminates the water quench, hydrogen contamination, and visibility problems that plague wet welding.

Quality Factor	Dry Hyperbaric Weld	Wet Weld
Tensile Strength	Comparable to surface welds	10-20% lower than surface welds
HAZ Hardness	Comparable to surface welds	Significantly higher (300-450 HV)
Hydrogen Content	Low (similar to surface low-hydrogen welding)	Very high (30-80 mL/100g)
Porosity	Minimal (standard defect rates)	Significant (inherent to process)
Ductility	Comparable to surface welds	Reduced (lower elongation)
Inspection Results	Can meet surface welding standards	Requires relaxed acceptance criteria (AWS D3.6 Class B or C)

Processes Used in Dry Hyperbaric Welding

GTAW (TIG): The preferred process for critical pipeline and subsea repairs. TIG produces the highest-quality welds with precise heat control. The helium-rich atmosphere inside the habitat at depth actually improves TIG arc characteristics on some materials.

GMAW (MIG): Used for higher deposition rates on fill and cap passes after a TIG root. Pulse MIG works well in the pressurized habitat environment.

SMAW (Stick): Used for some applications, particularly with E7018 electrodes. The controlled atmosphere allows low-hydrogen electrodes to perform as intended, unlike wet welding where water destroys the low-hydrogen benefit.

FCAW: Flux-cored wire is used for fill passes where high deposition rate is needed and the joint geometry allows.

Habitat Types

Full enclosure habitat: Completely surrounds the workpiece, providing a large dry workspace. Used for complex repairs requiring extended welding time and multiple processes.

Open-bottom habitat (wet bell): A smaller enclosure open at the bottom, with gas pressure holding the water surface below the work area. Simpler and cheaper to deploy but provides less workspace.

Cofferdam (dry chamber): A sealed chamber that can be pumped completely dry, used for shallow-water applications where full dewatering is practical.

Cost Comparison

The cost difference between wet and dry underwater welding drives most project decisions. Dry welding costs significantly more because of the habitat fabrication, deployment, and operational overhead.

Cost Category	Wet Welding	Dry Hyperbaric Welding
Mobilization	$10,000-50,000	$100,000-500,000+
Habitat/Equipment	None (standard dive equipment)	$50,000-300,000+ per project
Daily Spread Rate	$5,000-20,000/day	$50,000-200,000+/day (sat diving vessel)
Dive Team Size	4-6 person dive team	12-20+ person team (sat diving crew)
Typical Project Duration	Days to weeks	Weeks to months
Weld Quality Achieved	AWS D3.6 Class B or C	AWS D3.6 Class A (surface equivalent)

The daily spread rate for a saturation diving vessel with habitat welding capability can exceed $150,000-200,000/day. This includes the vessel charter, crew, life support systems, gas supply, and diving equipment. A dry welding project on a deepwater pipeline might cost $2-10 million for a single repair.

Wet welding a similar joint might cost $50,000-200,000. The quality difference is dramatic, but so is the cost difference.

When to Use Each Method

Wet Welding Applications

Wet welding is appropriate when:

The repair is temporary or non-structural
The application doesn’t require surface-quality welds
Speed of mobilization is critical (emergency repairs)
Water depth is less than 150 feet
Cost constraints make dry welding impractical
The structure has redundant load paths (one member failure doesn’t cause collapse)

Common wet welding applications:

Emergency repairs to maintain structural integrity until a permanent fix is planned
Cathodic protection anode installation
Doubler plate installation for temporary reinforcement
Cofferdam and sheet pile repairs
Dock and pier maintenance
Non-critical structural member repair on offshore platforms

Dry Hyperbaric Welding Applications

Dry welding is required when:

The weld must meet surface welding quality standards (AWS D3.6 Class A)
The application is structural or pressure-containing
Regulatory requirements mandate surface-quality welds
The depth exceeds wet welding’s practical limit
Long-term integrity of the repair is critical

Common dry welding applications:

Subsea pipeline repair and tie-ins
Offshore platform structural repairs (permanent)
Riser and caisson repairs
Subsea valve and manifold repair
Nuclear power plant underwater repairs (containment structures)

AWS D3.6: Underwater Welding Code

AWS D3.6M, “Underwater Welding Code,” governs both wet and dry underwater welding. It establishes three classes of underwater welds:

Class	Quality Level	Application	Method
Class A	Comparable to surface welding codes	Structural, pressure-containing, permanent	Dry hyperbaric (required)
Class B	Limited-quality, suitable for specific applications	Non-critical structural, temporary repairs	Wet or dry
Class C	Lowest quality, limited structural value	Non-structural, temporary	Wet (typical)

Class A underwater welds must meet the same acceptance criteria as the applicable surface welding code (D1.1, API 1104, ASME IX, etc.). This level of quality is only achievable through dry hyperbaric welding.

Class B welds acknowledge the inherent limitations of wet welding and provide relaxed acceptance criteria that account for higher porosity, reduced ductility, and elevated hardness. The engineer must determine whether Class B quality is adequate for the specific application.

Class C welds have the most relaxed criteria and are essentially limited to non-structural or temporary applications where any welded attachment is better than no attachment.

Qualification Requirements

AWS D3.6 requires both procedure qualification and welder qualification for underwater welding. The qualification testing must be performed at the depth and conditions representative of the production work. A wet welding qualification at 30 feet does not qualify for wet welding at 150 feet because the increased pressure changes the welding characteristics.

The choice between wet and dry underwater welding isn’t really a choice in many cases. The specification, classification society rules, or regulatory requirements dictate the method. When both are technically acceptable, cost drives the decision. When quality drives the decision, dry hyperbaric welding wins every time.

Back to underwater welding for more underwater welding topics. See also underwater welding salary and career for the career side of this specialty.

Frequently Asked Questions

Which produces better welds, wet or dry underwater welding?

Dry hyperbaric welding produces significantly better welds than wet welding. Inside a pressurized habitat, the welding environment is essentially the same as surface conditions (dry, controlled atmosphere, stable arc). Dry welds can meet the same quality standards as surface welds. Wet welds have inherently lower quality due to rapid quenching by surrounding water, hydrogen embrittlement from water dissociation, porosity from steam and gas generation, and limited visibility for the welder.

What electrodes are used for wet welding?

Wet welding uses modified E6013 or E7014 stick electrodes with waterproof flux coatings. The waterproof coating prevents the flux from absorbing water before it reaches the arc. The electrodes run on DCEN (electrode negative) polarity, which is opposite to standard surface stick welding. Some manufacturers produce specially formulated wet welding electrodes with coatings designed to displace water from the arc zone and reduce hydrogen absorption.

How deep can wet welding be performed?

Wet welding has been performed at depths exceeding 300 feet (91 meters), but quality and productivity decrease significantly below 100 feet (30 meters). As depth increases, ambient pressure compresses the arc, increases quench rate, and makes electrode manipulation more difficult. Most production wet welding is done at depths less than 200 feet. Below 300 feet, dry hyperbaric welding is strongly preferred for any structural application because wet weld quality degrades to the point where structural integrity can't be reliably achieved.