Application of Clad Plate in Marine Scrubbers: An Engineering Solution for Cost Reduction Without Performance Compromise

The implementation of IMO's sulfur cap has been in effect for several years, and most shipowners have already installed scrubbers. However, the industry's focus has recently shifted from "whether to install" to "what materials to use" — as the material cost of scrubbers has become a significant economic burden.

The internal structure of a scrubber must withstand high-temperature flue gas at 200–400°C, as well as the strong acid corrosion generated by the reaction between seawater and sulfur oxides. Conventional solutions typically use all-special-alloy structures, such as UNS S32750, UNS S31254, or titanium (ASTM B265 Grade 2). While these materials offer excellent corrosion resistance, their price per unit weight is 12 to 30 times that of ordinary carbon steel such as ASTM A36 or ASME SA516 Grade 70. Building a scrubber entirely from special alloys can consume a considerable portion of a vessel's propulsion system cost, just in material expenses.

The clad plate solution has emerged as a logical alternative. Its core principle is simple: corrosion occurs only on the internal wall of the tower, while the external structure is not exposed to corrosive media. An all-special-alloy approach therefore represents unnecessary material over-specification. A clad plate adopts a double-layer structure — a thin inner layer of special alloy (e.g., ASTM B265 Grade 2 titanium or ASTM B575 Grade C-276 nickel alloy) responsible for corrosion resistance, and an outer layer of ordinary carbon steel (e.g., ASTM A36 or ASME SA516 Grade 70) providing structural strength. The two layers are metallurgically bonded through explosive cladding or roll bonding, without delamination or peeling.

From an economic perspective, with a mass ratio of carbon steel to special stainless steel of 3:1, material cost can be reduced by 60% to 75%. This is not a material downgrade, but a precise material selection based on service conditions.

However, the core challenge of the clad plate solution lies in quality assurance. Given the harsh service environment of scrubbers, any blistering, delamination, or cracking in the clad layer could lead to more complex consequences than the failure of a single-material structure.

Scrubber

FUGO TECH ensures quality from three dimensions: standards, testing, and certification.

On standards: FUGO TECH simultaneously complies with ASTM, GB, and EN standards, applying the most stringent requirements among them as the internal execution benchmark. For the cladding layer, materials conform to ASTM B265 (titanium), ASTM B575 (nickel alloys), or ASTM A240 (stainless steels). For the backing steel, materials conform to ASTM A36 or ASME SA516. Clad plates dedicated to marine scrubbers must also meet CCS (China Classification Society) rules, China's ship inspection requirements, and GB/T 43109-2023 "Stainless steel clad plates for ship and offshore engineering applications" — a Chinese national standard, specifically addressing ship and offshore engineering scenarios, with clear provisions on impact toughness, intergranular corrosion, and pitting corrosion. FUGO TECH's products have completed all these verifications before leaving the factory.

On testing: Incoming raw materials undergo re-inspection of chemical composition per applicable ASTM reference standards, mechanical properties, and surface quality. The surface oxide film condition of titanium plates directly affects the quality of explosive cladding; defective incoming materials are rejected outright. After explosive cladding, full-surface ultrasonic testing is performed first. The area within 50mm of the edge must be 100% covered with no allowable unbonded zones. Destructive testing follows — specimens are cut from each batch for shear strength testing (above 140 MPa per ASTM A264 or A265), bending tests (per ASTM A263), and tensile tests (per ASTM A370). Corrosion resistance is separately verified through neutral salt spray testing per ASTM B117 or ISO 9227, with a duration of no less than 2,000 hours.

On certification: FUGO TECH assigns a unique code to each clad plate, enabling full traceability from raw material batch number, cladding parameters, heat treatment curve, to ultrasonic test reports. Upon delivery, a complete set of quality documentation is provided, including CCS certificates, mechanical property reports, non-destructive testing reports, and corrosion test reports. Where applicable, an ASTM test certificate (per A263/A264/A265) is also furnished.

In addition to the quality assurance system, the applicability of clad plates under specific scrubber operating conditions requires careful evaluation. In the hot-wet zone (flue gas inlet section), temperatures cycle between ambient temperature (when the system is off) and 400°C (during operation). Such cyclic temperature variations generate significant thermal stress between the clad layers. FUGO TECH performs thermal stress simulation assessments before project delivery, and only allows the use of clad plates in the hot-wet zone after confirming the feasibility of the solution. In the warm-wet and cold-dry zones, where operating conditions are relatively stable, the applicability of clad plates is well validated.

Repairability is another aspect worth attention. If the inner wall of a clad plate is damaged, repair work requires proficiency in welding processes for both carbon steel and special alloy — a technical capability rarely available in a shipboard operating environment. FUGO TECH introduces a "directional corrosion control" strategy at the vessel design stage. Even if local damage occurs on the inner wall, corrosion will not propagate through the thickness into the structural interior, providing shipowners with sufficient time to schedule dock repairs.

The material selection for marine scrubbers is essentially an engineering balance between "fitness for purpose" and "over-engineering." All-special-alloy solutions are technically the safest, but the material cost is significantly higher. The clad plate solution substantially reduces material cost while maintaining corrosion resistance, making it particularly suitable for cost-sensitive projects with manageable operating conditions. Through systematic implementation of standards, testing procedures, and certification management, FUGO TECH ensures that every clad plate delivered meets the demanding service requirements of marine scrubbers.

Learn more about Fugo Clad plate, please visit https://www.fugo-tech.com/clad-plate/.