{"id":3475,"date":"2026-10-09T02:25:00","date_gmt":"2026-10-08T18:25:00","guid":{"rendered":"http:\/\/www.baaclottobet.com\/blog\/?p=3475"},"modified":"2026-10-09T02:25:00","modified_gmt":"2026-10-08T18:25:00","slug":"how-does-sodium-hydrosulphide-70-affect-the-corrosion-of-equipment-4e06-ca7f4b","status":"publish","type":"post","link":"http:\/\/www.baaclottobet.com\/blog\/2026\/10\/09\/how-does-sodium-hydrosulphide-70-affect-the-corrosion-of-equipment-4e06-ca7f4b\/","title":{"rendered":"How does Sodium Hydrosulphide 70% affect the corrosion of equipment?"},"content":{"rendered":"

As someone who\u2019s spent nearly a decade on the production floor and in customer consultations as a sodium hydrosulphide (NaHS) 70% supplier, I\u2019ve lost count of how often I get asked a single question\u2014usually by a plant engineer mid-call, when their equipment is already showing early signs of rust: Does this stuff eat through our pipes, reactors, and storage tanks, or is it manageable? For too long, there\u2019s been a messy mix of fear and half-formed assumptions around NaHS 70% and its impact on corrosion, and I wanted to break down what I\u2019ve learned firsthand, no textbook jargon that\u2019ll make you zone out. Sodium Hydrosulphide 70%<\/a><\/p>\n

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First, let\u2019s ground this in what NaHS 70% actually is, because a lot of the confusion starts here. Most people who don\u2019t work with it daily don\u2019t realize this isn\u2019t the same as the smelly, dilute solution you might encounter in a high school chem lab. Our 70% grade is a solid, flake-like product (technically an anhydrous or near-anhydrous blend\u2014we control moisture content super tightly) that\u2019s dissolved into water for 90% of industrial uses. That concentration is the sweet spot for customers in mining, pulp and paper, oil and gas, and wastewater treatment, because it\u2019s more transportable, has a longer shelf life than lower grades, and cuts down on shipping and storage volume. But here\u2019s the critical part: when it\u2019s dissolved into process water, it doesn\u2019t stay as neat NaHS. It breaks down into hydrogen sulphide (H\u2082S), sodium ions (Na\u207a), and hydroxide ions (OH\u207b)\u2014and that\u2019s the mix that interacts with metal surfaces.<\/p>\n

Let\u2019s start with the \u201cbad\u201d side, because that\u2019s where the concern lives. A common scenario I walk customers through is a gold leaching plant in Nevada that called us two years ago. They\u2019d been using a competitor\u2019s 60% NaHS grade for three months, and their carbon steel leaching tanks were developing pitting corrosion within 18 months of installation. When we sent a field technician to check, here\u2019s what we found: their process water was slightly acidic (pH 5.8), so when they diluted the competitor\u2019s product, the breakdown of NaHS produced a lot more H\u2082S gas that didn\u2019t stay dissolved. That H\u2082S reacted with iron in the steel to form iron sulphide (FeS) deposits, but the problem was the porosity of those deposits. Instead of forming a tight, protective layer over the steel, the FeS flakes left gaps\u2014so the underlying metal was exposed, and the acidic process water plus continued reaction created localized pitting that ate through the tank walls. The competitor\u2019s lower-grade product had more impurities, like free sulphur and small amounts of sodium sulphate, that sped up that breakdown; our 70% grade, with 99% purity, doesn\u2019t have those extra contaminants to throw the reaction off.<\/p>\n

Wait, but that\u2019s not the whole story, right? I\u2019ve also seen plants where NaHS 70% was added, and corrosion rates dropped. A pulp mill in the Pacific Northwest switched to our NaHS grade in 2021 for their black liquor recovery process, and their stainless steel evaporators went from 0.2 mm of corrosion per year to 0.06 mm. How? Let\u2019s talk about pH and material compatibility. NaHS is an alkaline product\u2014when dissolved in water, it raises the pH. If the process environment is already slightly alkaline (pH 7.5 to 9, which is common in many industrial processes), the OH\u207b ions from NaHS dissolve react with the surface of carbon steel to form a thin, passive layer of iron hydroxide (Fe(OH)\u2082) and then magnetite (Fe\u2083O\u2084). That layer acts as a barrier, keeping water and other corrosive agents from reaching the metal. It\u2019s not a permanent shield, but it\u2019s enough to slow general corrosion down drastically, not speed it up. The H\u2082S from NaHS breaks down under alkaline conditions too, forming sulphide ions that react with iron to form FeS\u2014but this time, if the pH is controlled, the FeS layer is dense and adheres to the passive layer, reinforcing it instead of puncturing it.<\/p>\n

So why the conflicting results? The biggest mistake customers make is not matching their NaHS grade and handling to their specific process conditions. Let\u2019s break down the three main variables that determine how NaHS 70% affects corrosion, because this is the part I wish more process engineers paid attention to.<\/p>\n

First variable: pH of the process stream. This is non-negotiable. If your process is acidic (pH < 7), NaHS will react with the excess H\u207a ions to produce large amounts of dissolved H\u2082S, which can escape as gas. That\u2019s when you get pitting, as the H\u2082S reacts with iron to form porous FeS. If your process is alkaline (pH > 8.5), the H\u2082S stays dissolved as sulphide ions, which form that protective FeS layer. I remember a copper mining operation in Arizona that was operating at pH 6.2 when they first tried NaHS; their corrosion rates spiked. We suggested they adjust their process pH up to 7.8 with a small dose of caustic soda, and switch to our 70% grade (instead of their previous 50% grade that had more free acid impurities). Within six months, their pitting corrosion stopped entirely. They ended up placing a bulk order that\u2019s been renewing every quarter since.<\/p>\n

Second variable: material of construction. Not all metals react the same way with NaHS. Carbon steel is tricky, like the Nevada gold plant found\u2014if pH is low, carbon steel corrodes fast, but at high pH, it forms that protective layer. Stainless steel is a different animal. 304 and 316 stainless, the two most common grades in industrial equipment, actually handle NaHS well if there\u2019s not too much H\u2082S present, but wait\u2014if H\u2082S levels are very high (over 100 ppm) and the pH is between 4 and 7, stainless steel can suffer from stress corrosion cracking (SCC). That\u2019s a sneaky type of corrosion where small cracks form under the surface, often without visible warning, which is way more dangerous than general pitting. We\u2019ve seen this in oil and gas pipelines that use NaHS for sour gas treating, where H\u2082S levels are high\u2014they had to switch to alloy 22 or duplex stainless steel to prevent that. On the flip side, copper and brass? They\u2019re highly susceptible to corrosion from NaHS, full stop. If you have copper pipes in your process, NaHS 70% will eat through them rapidly, no matter the pH\u2014we always recommend switching to HDPE or lined steel for lines that carry NaHS, even for short runs.<\/p>\n

Third variable: impurities in the NaHS product. This is where our 70% grade stands out, because we test every batch to ensure it\u2019s at least 99% pure, with less than 0.5% total impurities (free sulphur, sodium sulphide, moisture). A lot of lower-grade NaHS (like 50% or 60% products from some manufacturers) have 3-5% impurities, which include elemental sulphur. That free sulphur reacts with NaHS in solution to form polysulphides, which are way more corrosive than regular sulphide ions. The Nevada gold plant\u2019s issue? Their competitor\u2019s product had 2.8% free sulphur, which made their H\u2082S production way higher and the FeS layer porous. Our 70% grade has less than 0.3% free sulphur, so that reaction doesn\u2019t happen. I once got a call from a chemical processor that had been using a European NaHS grade; their reactor was corroding at 0.5 mm\/year. We sent a 100 kg trial of our 70% grade, and they tested it and found their corrosion rate dropped to 0.12 mm\/year\u2014all because the impurities were gone.<\/p>\n

Now, let\u2019s talk about real-world best practices that I\u2019ve shared with dozens of customers, because this is what prevents corrosion issues, not just theoretical science. First, always test your NaHS batch before full-scale use. A small 500 ml lab test can tell you how your specific process water will react with our 70% grade\u2014measure pH before and after adding NaHS, test for H\u2082S levels, and do a quick corrosion coupon test with your equipment\u2019s material of construction. Second, control pH within that sweet spot of 7.5 to 9 for most applications. If your process naturally runs acidic, add a small amount of caustic soda along with NaHS to adjust it\u2014this is a small cost that saves tens of thousands in equipment repairs. Third, monitor H\u2082S levels regularly, especially in enclosed spaces where H\u2082S gas can build up (it\u2019s toxic, too, so safety is a double win). If H\u2082S levels are over 100 ppm, you might need to adjust your NaHS feed rate or upgrade your material to a higher alloy. Fourth, store NaHS 70% correctly\u2014keep it in tightly sealed, lined steel drums or tanks, because moisture exposure can cause it to degrade, releasing more H\u2082S and impurities that accelerate corrosion. We always give customers a free storage guide when they place their first order, because even the best product will cause issues if it\u2019s stored wrong.<\/p>\n

I want to be transparent here\u2014NaHS 70% isn\u2019t a corrosion cure-all. It\u2019s a chemical that interacts with metal surfaces, and whether it helps or hurts depends entirely on how you use it. I\u2019ve had customers come to me thinking NaHS is evil, only to adjust their pH and material, and see their corrosion problems vanish. I\u2019ve also had customers who used it wrong for years, and had to replace their entire tank farm because they didn\u2019t understand the variables. That\u2019s why as a supplier, we don\u2019t just sell you a bag or drum of NaHS\u2014we offer free process consultations, send field technicians to check your equipment if you\u2019re having issues, and work with you to tailor the product and handling to your specific operations. We don\u2019t push our 70% grade if it\u2019s not the right fit\u2014if you only need NaHS for a small process that runs at very low pH, we\u2019ll recommend a lower-grade product that works better for you, because we want long-term partnerships, not one-off sales.<\/p>\n

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If you\u2019re dealing with corrosion related to sodium hydrosulphide 70%, or just want to optimize your process to avoid future issues, we\u2019re here to help. You can reach out to our team to discuss your specific needs, get a custom quote for bulk or small orders, or schedule a free process assessment. Don\u2019t wait until a small rust spot turns into a costly equipment failure\u2014let\u2019s work together to find the right solution for your operations.<\/p>\n

Sodium Tripolyphosphate(STPP)<\/a> References<\/p>\n