Laboratory tests are not strictly comparable with actual service conditions, where the corroding medium often contains impurities. These may in some cases increase corrosion, in others decrease it. In unfavorable cases, the increase can be very great.
Before making the final selection of material, therefore, it is in many cases necessary to make tests. The best results of laboratory tests are obtained if the solution used is identical with that which occurs in practice. This includes any effect impurities may have on corrosion. It is even better to expose test pieces to the actual process or environment concerned. Weighing and microscopical examination of the test specimens after a certain period of exposure will give a good idea of the corrosion risks to be expected.
When there is some doubt about the material selection, it is always advisable to contact us. It is very important to furnish full information about the corrosion conditions concerned. The following information is necessary:
Information concerning the type of structure, preferably with sketches, drawings or process descriptions, previously used materials, flow velocities, temperature variations, service life requirements etc., is also very valuable.
These corrosion tables use a number of symbols, having the following meanings:
|0||Corrosion rate less than 0.1 mm/year. The material is corrosion proof.|
|1||Corrosion rate 0.1—1.0 mm/year. The material is not corrosion proof, but useful in certain cases.|
|2||Corrosion rate over 1.0 mm/year. Serious corrosion. The material is not usable.|
|p, P||Risk (severe risk) of pitting and crevice corrosion.|
|c, C||Risk (Severe risk) of crevice corrosion. Used when there is a risk of localised corrosion only if crevices are present. Under more severe conditions, when there is also a risk of pitting corrosion, the symbols p or P are used instead.|
|s, S||Risk (Severe risk) of stress corrosion cracking.|
|ig||Risk of intergranular corrosion.|
|ND||No data. (Used only where there are no actual data to estimate the risk of localised corrosion instead of p or s).|
Disclaimer: Laboratory tests are not strictly comparable with actual service conditions. Accordingly, Alleima makes no warranties, express or implied, and accept no liability, compensatory or consequential, for the performance of different materials in individual applications that may be based on the information provided in this publication.