The main distinction between 304 and 316 stainless steel pipe is that 316 accommodates 2%-3% molybdenum and 304 has no molybdenum. The “moly” is added to improve the corrosion resistance to chlorides (like sea water). So, whereas 316 stainless steel pipe is mostly considered more corrosion resistant than 304, relying on the character of the corrosive media the corrosion charges of 304 and 316 might be related.

Generally, SS 304/304L is assumed to be corrosion-resistant material. But after we come to Piping Specs with SS 304/304L MOC, its worth is taken as 0.063 inches — identical for SS316/316L . Please explain.

We now have a plant that produces fertilizer. In one part we combine 40% phosphoric acid and 98% sulfuric acid together in a ratio of 75-80 : 25-20 phosphoric acid:sulfuric acid. After that the mixture is cooled to a temperature of eighty degrees C. What is the most effective material of building for transfer piping? The existing material, 304 stainless steel pipe, reveals issues at the welds.

From a supplies of development perspective, seamless steel tube this is a tricky mixture to deal with, especially at eighty degrees C and better. Phosphoric acid is less corrosive than sulfuric acid. Pure phosphoric acid has no oxidizing power however business phosphoric acid accommodates impurities such as fluorides and chlorides that may significantly increase its corrosivity. When you have virtually any inquiries with regards to in which in addition to how to make use of steel tubing wholesale, you’ll be able to e mail us in our page. The corrosivity of sulfuric acid is dependent upon many components including temperature, concentration, the presence of oxidizing or lowering impurities, velocity effects, and solids in suspension.

It’s normally not sensible to pick out supplies of construction for sulfuric acid dealing with equipment primarily based only on published corrosion information since corrosion by sulfuric acid is a posh phenomenon. Small variations in impurities, velocity, or focus can significantly impression the corrosion price. Halides usually enhance corrosion whereas aeration or the presence of oxidizing brokers normally will increase the corrosion price of non-ferrous materials and reduces the corrosion rates of stainless steel pipe alloys. I strongly suggest laboratory corrosion research be run in your particular stream as part of your materials of development choice process.

I have a large storage tank of 93% sulfuric acid. I am having excessive corrosion of the highest of the 4-inch carbon steel outlet pipe. I’m thinking of replacing the outlet pipe with Schedule one hundred twenty carbon steel pipe. Is there any more resistant materials, insert, or coating you possibly can recommend for increased life?

Carbon steels are only acceptable for 93% sulfuric acid when fluid velocity is low (< 3 ft/sec). For 4-inch diameter piping or less with velocities up to 5.9 ft/sec, 316L stainless steel pipe is a good choice. For velocities higher than 5.9 ft/sec, Alloy 20Cb-3 (UNS N08020) has been used successfully. For additional information, consult NACE Recommended Practice RP-0391 "Materials for the Handling and Storage of Commercial Concentrated (90 to 100%) Sulfuric Acid at Ambient Temperatures."

In your question, you stated you are experiencing problems with 304 stainless steel pipe on the welds. If this is the case, you might consider transferring to 304L stainless steel pipe. Low carbon variations of austenitic Stainless steel seamless pipe like 304L are designed to remove problems associated with carbide precipitation and chromium depletion at welds. If 304L does not work, strive progressively moving as much as the next alloy. Possible candidate supplies in order of usually rising corrosion resistance are: 316L stainless steel pipe, 20-kind alloys like 20Cb-3, increased chromium Fe-Ni-Mo alloys like Alloy 31, and nickel-base molybdenum-chromium alloys like C-276.