PRODUCTS

Coastal structures

Long-term anticorrosion technology for steel structures, such as jackets, constructed in coastal areas

Corrosion prevention using seawater-resistant stainless steel

Compared with land structures, coastal steel structures are exposed to a severe corrosive environment and, therefore principally adopt an anticorrosion process as shown in the figure on the right.

Super high build coating (coating protection) and cathodic protection have been used to protect jackets constructed in coastal areas from corrosion. Recently, however, an anticorrosion process using seawater-resistant stainless steel for a portion of the corrosion prevention (stainless steel lining) has been adopted for LCC.
This stainless steel lining can be applied to areas that have been protected with the super high build coating. In general, stainless steel lining is laid on the flat and smooth areas of the steel pipes of jackets, and the super high build coating is applied to complicated areas such as the girders and the tubular joints.

<Conventional anticorrosion process>

Areas above LWL-1.0 m
・Super high build coating
Organic zinc-rich primer: 20 μm thick
Super high build epoxy resin paint: 2500 μm thick

Areas below LWL-1.0 m
・Cathodic protection (galvanic anode method)

Anticorrosion process using stainless steel lining>

Areas above LWL-1.0 m
・Super high build coating (girders, panel points)
Organic zinc-rich primer: 20 μm thick
Super high build epoxy resin paint: 2500 μm thick
・Stainless steel lining (flat and smooth areas of steel pipes)
 Material: JIS G 4305 SUS312L, sheet thickness: 0.4 mm or over

Areas below LWL-1.0 m
・Cathodic protection (galvanic anode method)

Characteristics of corrosion prevention using stainless steel lining

(1) Distinguished corrosion resistance in very corrosive tidal zones and splash zones
(2) Outstanding impact resistance and abrasion resistance against the collision of floating solids
(3) Reduced life cycle cost
(4) Stable lining quality
(5) Increasing applications for important new port steel structures
( J acket construction track record : Oo i Wharf, Hakata Island City, Runway D of Haneda Airport)

Service life

The Corrosion Prevention and Repair Manual for Port and Harbor Steel Structures (Coastal Development Institute of Technology: 2009) stipulates the expected service life of anticorrosion processes for LCC calculations. According to the manual, the anticorrosion period of heavy-duty anticorrosion coating and super high build coating used for steel pipe piles and jackets is about 30 years, whereas that of stainless steel lining is estimated to be as long as 50 years. Haneda Airport has adopted stainless steel lining as an anticorrosion process that can serve for 100 years.

Material

The material used for stainless steel lining is seawater-resistant stainless steel, which is overwhelmingly superior in corrosion resistance to general types of stainless steel (SUS304 series, SUS316 series) due to its increased amount of such corrosion-resistant alloy elements as Cr and Mo. This stainless steel is used for seawater desalination plants and heat exchangers, and matches titanium in corrosion resistance in the natural environment.

Corrosion prevention using stainless clad steel

Unlike the coating protection applied to steel structures, stainless clad steel is a material combined with stainless steel at the time of steel sheets manufacturing.