Millions of miles of pipelines are used to transmit drinking water around the world. These pipelines must have good corrosion resistance to water itself, soil chemicals and treatment chemicals, so as to ensure adequate service life and provide sanitary drinking water. Type 316 (2-3%Mo) stainless steel has been proven to provide adequate corrosion resistance in most applications, and is more competitive than other piping materials. If additional corrosion protection is required, for example, in the installation of coastline, duplex stainless steel (3.0-3.5%Mo) can be used to achieve the required sanitary conditions and service life.
As for the reasons, I have learned the following summary of the beneficial properties of molybdenum bearing stainless steel below.
The first is excellent corrosion resistance. Stainless steel is more resistant to oxidation of water and biocide than carbon steel and cast iron or ductile iron. This leads to longer service life of stainless steel water pipelines.
Followed by corrosion protection, stainless steel does not require internal and external coatings, nor does it require cathodic protection. This will reduce the cost of the system and make the stainless steel more compatible with the environment.
The third is hygienic material. Because of its very high oxide film stability, stainless steel water pipelines are basically inert in water. The leaching of alloying elements (Cr and Ni) is within the safety limits. Therefore, stainless steel pipelines can provide better drinking water quality.
The fourth is friction coefficient. Compared with cement lined carbon steel pipeline or corroded carbon steel, the friction loss of stainless steel pipeline leads to smaller hydraulic pressure along the pipeline. This provides the opportunity to reduce the inner diameter of the pipeline and save capital costs. This is also the reason for lower sediment adhesion and lower bacterial colonization. They can also provide higher traffic.
The fifth is good strength and ductility. Stainless steel pipelines, especially duplex stainless steel, have higher mechanical properties compared with carbon steel and cast iron pipelines. This can reduce the wall thickness of the water pipeline (no need for any corrosion allowance), thereby saving investment costs. Better ductility is also important in terms of safety, such as in the case of earthquakes.
The sixth is erosion corrosion performance. Duplex stainless steel is more resistant to corrosion and corrosion than carbon steel, especially if there is sand in the surrounding environment.
Seventh is easy to make. Stainless steel is an adaptable material. It is easy to form, machine and weld. It is easy to install and modify the pipeline with its good ductility. They also have a variety of product forms.
In addition, the stainless steel pipelines are easy to maintain, with high corrosion resistance and easily weldability, the probability of water leakage will be reduced greatly, and it may be reduced from 25% to less than 5%, which will further reduce the cost. This argument is becoming more and more important because of the increasing cost of water and water treatment.
There is also good durability, because SS can resist crevice corrosion, cavitation and wear in pure and polluted waters, as well as in the atmosphere (and even pollutants). It is cost-effective for long-term use and will not cause environmental pollution.
The last one is recyclable, stainless steel is 100% recyclable, and part of its initial cost may be recovered during recycling.
Source: China Stainless Steel Water Pipeline Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)