Hot Rolled Steel
Types and Durability
|
Description Hot Rolled Steel |
Expected Lifespan ( Years ) |
Adjustment Factors
|
|
|
External
|
Internal
|
||
| Mild steel, hot dipped galvanised after any cutting, welding or drilling to BS 5493 specification SB3 (equivalent in either case to a zinc coating weight of 1500g/m² or 210 micron thickness). |
30
|
35+
|
1st stage adjustment factor:
In industrial areas (heavy polluted): -15% of no. of years In urban areas: -10% of no. of years In suburban areas: no adjustment 2nd stage adjustment factor: Structural members subjected to ‘very severe’ exposure conditions to Table 3.2 of BS 8110:Part 1, without additional surface protection: -30% of no. of years. Within 20m from express way: -20% of no. of years Within 20m from major arterial road: -10% of no. of years Within 20m from light traffic road: – 5% of no. of years Test certificate from approved local testing authority : +15% of no. of years |
| Mild steel, hot dipped galvanized after any cutting, welding or drilling to SB2 (equivalent in either case to a zinc coating weight of 1000g/m² or 140 micron thickness). |
25
|
35+
|
|
| Mild steel, molten zinc sprayed after any cutting, welding or drilling to BS 5493 specification SC2Z (equivalent to a zinc coating weight of about 1050g/m² or 150 micron thickness). |
25
|
35+
|
|
| Mild steel, molten zinc sprayed after any cutting, welding or drilling to BS 5493 specification SC1Z (equivalent to a zinc coating weight of about 700g/m² or 100 micron thickness). |
20
|
35+
|
|
| Mild steel, hot dipped galvanized after any cutting, welding or drilling to BS EN 729 (to steel at least 5mm thick) or to BS 5493 specification SB1 ( any thickness steel) equivalent in either case to a zinc coating weight of 610g/m² or 85 micron thickness. |
20
|
35
|
|
| Mild steel, hot dipped galvanized after any cutting, welding or drilling to BS EN 729 to steel 2mm – 4.9mm thick (equivalent to a zinc coating weight of 460g/m² or 64 micron thickness). |
15
|
30
|
|
| Mild steel, hot dipped galvanized after any cutting, welding or drilling to BS EN 729 to steel 1mm – 1.9mm thick (equivalent to a zinc coating weight of 335g/m² or 43 micron thickness). |
10
|
25
|
|
| Mild steel, blast cleaned after any cutting, welding or drilling and protected with an appropriate Micaceous Iron Oxide, Chlorinated Rubber or similar high performance finish to give a minimum dry film thickness of 250 microns. |
10
|
25
|
|
Combination of adjustment factors (1st stage and 2nd stage) should be added to obtain the durability values. Refer to durability calculator.
Corrosion life of unpainted steel in atmospheric environment
| Atmospheric classification | Short term
(2-5 years) |
Medium term
(5-10 years) |
Long term
(10-20 years) |
| Mild | Suitable | Suitable | Suitable |
| Moderate | Suitable | Suitable | Suitable |
| Tropical* | Suitable | Suitable | Suitable |
| Industrial | Unsuitable | Unsuitable | Unsuitable |
| Marine | Suitable | Unsuitable | Unsuitable |
| Severe Marine | Unsuitable | Unsuitable | Unsuitable |
* Not suitable when affected by sea salt spray
Notes:
- Weights of zinc coatings are for any one face only.
- The range of options for protecting steel is huge, therefore the classes listed are indicative only.
- The lives and classes included are intended for solid sections only; the complications of protecting hollow sections (to avoid internal corrosion) have been ignored for simplicity.
Key durability issues
Type/thickness of surface protection, exposure conditions.