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Specification options
Steelwork exposed to atmosphere	Capital cost £/m²	Lifecycle cost for 50 or 120 years £/m²	Period to first major maintenance years
Category 4: 50 years	Ìý	Ìý	Ìý
Hot dip galvanized to BS EN ISO 1461 mean coating thickness 85µm	35	42	80
Epoxy micaceous iron oxide (MIO) finish: 100µm; Zinc phosphate epoxy primer: 80µm. Steel: blast cleaned to Sa 2.5	22	61	20
High solids polyurethane finish:100µm. inc phosphate epoxy primer: 100µm. Steel: blast cleaned to Sa 2.5	17	48	20
Category 5: 120 years	Ìý	Ìý	Ìý
Hot dip galvanized to BS EN ISO 1461 mean coating thickness 85µm	35	43	80
Hot dip galvanized mean coating thickness 140µm includes shotblast preparation	50	58	120
Epoxy micaceous iron oxide (MIO) finish: 100µm; Zinc phosphate epoxy primer: 80µm. Steel: blast cleaned to Sa 2.5	22	73	20
High solids polyurethane finish:100µm. Zinc phosphate epoxy primer: 100µm. Steel: blast cleaned to Sa 2.5	17	57	20
Table notes: External environment category C3 to ISO 9223, Average annual zinc corrosion rate: 1µm/yr. First protective system factory applied. Subsequent coating assumed at 8-10 year intervals including allowance for treating corosion and quinquennial inspections. Dimensions refer to dry film thicknesses. Discount rates of 3.0% (50 years) and 2.5% (120 years) are used to calculate net present values. There are a huge range of alternative coating systems; costs and options are indicative. Use specialist advice for suitable options and a cost analysis based on project specific information for a realistic best value appraisal