Durability and Life Expectancy of Stainless Steel in External
Most important corrosion consideration with stainless steel is pitting corrosion. Micro pitting is manifested as surface rust staining and is generally considered unacceptable for a material basically selected for its aesthetic appearance and corrosion resistance.
Analysis and extrapolation of pit depth data gathered from atmospheric exposure test programs can be used as a durability guide. It must be borne in mind that staining from micro pitting may result in rejection of the steel on aesthetic grounds, long before pitting has perforated it.
Factors Affecting Durability
The durability of the stainless steel depends on:
steel grade
environment
surface finish
Chloride ions are the most aggressive environmental hazard when assessing the pitting corrosion risk. Marine sites tend to be the most aggressive and so give the lowest projected durability.
Acid conditions, sometimes found in industrialised atmospheres, are also aggressive. It is also important to consider the effects of local 'micro climates' that may influence how aggressive the environment is.
Estimated pit penetration times
The pitting life predictions shown in the table are based on a linear pit growth rate model.
| Location |
Estimated Time to Penetrate 1mm (Years) by steel type |
| 430(1.4016) |
304(1.4301) |
316(1.4401) |
| Marine |
N/A |
145 |
260 |
| Semi-industrial |
85 |
135 |
525 |
| Rural |
250 |
770 |
1200 |
The marine and rural site samples had 'mill' finishes and the semi-industrial site results had dull polished finishes.
The 1mm-perforation times for the 304 (1.4301) type are consistent with the projected design lives of most buildings.
It should be noted that the ferritic 430 (1.4016) type is not normally considered for building exterior applications, but is included in the table for comparison.
Corrosion | Metallographic Test | Metallographic Test Report | Stress Corrosion Cracking | Chloride SCC | Minimizing Chloride SCC | Stainless Steel Corrosion | Intergranular Corrosion | Stainless Steel Intergranular Corrosion | Corrosion of Piping | Corrosion Resistant Stainless Steel | Corrosion Resistant Material | Corrosion Resistance | Seawater Resistance | Corrosion Mechanism | Corrosion Process | Surface Coatings for Corrosion | Galvanic Corrosion | Galvanic Corrosion Risks | Causes of Metal Corrosion | Stainless Steel for Corrosion Resistance | ASTM A262 | ASTM E112 | Corrosion Resistance Table | Metals Corrosion Resistance | Oxidation Resistance | NACE MR0175/ISO 15156 | Carbon on Corrosion Resistance
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