Tag Archives: Corrosion

Over-sizing nuts to compensate for coated bolts

Posted on January 8, 2018 by dean

Q:  We have a corrosive application and we are debating on using coated carbon steel bolts and nuts or a solid corrosion resistant alloy. Obviously the coatings cost a lot less but we are unsure about how the coatings affect mechanical strength. A:  Coated bolts and nuts are typically undersized … Continue reading →

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Duplex 2507 bolts for high strength application in salt air

Posted on November 15, 2017 by dean

Q: I have a high strength application that requires resistance to damp salt air and occasional sea splash, I’m using Monel 400 but it’s not holding up the the 75ksi of yield I need. Lots of broken bolts? Is is corrosion or  strength? Thoughts? A: Your issue isn’t the corrosion. … Continue reading →

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AL6XN vs Monel bolts for salt water and marine use

Posted on November 14, 2017 by dean

Q: Is AL6XN a steel or nickel alloy? Trying to figure out if it would perform as well as Monel in seawater. A: To answer your first question, AL6XN bolts are actually both a nickel and a steel alloy. AL6XN is often described as a high nickel content stainless alloy. Though … Continue reading →

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Incoloy 825 vs Hastelloy C276 for Sour Gas

Posted on November 13, 2017 by dean

Q: I need bolts for a well pump exposed to sour gas? I’ve currently use Incoloy 825 bolts which works reasonably well, but I’m wondering if there is a better choice that is more economical and could offer equal or better corrosion resistance – any ideas? A: A great nickel alloy bolt … Continue reading →

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Nickel Alloys Part 1: Moderate Corrosion

Posted on November 2, 2017 by dean

Nickel alloys are a special class of metals containing high levels of nickel (often greater than 20%). They play a key role in industry for their unique combination of high strength, corrosion resistance to harsh acids (like hydrochloric and sulfuric) and high temperature stability. This two-part newsletter will help summarize the distinct benefits of the … Continue reading →

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Corrosion resistance of Inconel 625 bolts vs Hastelloy C276

Posted on August 28, 2017 by dean

Q: Inconel 625 and Hastelloy C276 bolts seem to have similar Nickel content. Does this mean these fasteners will perform the same in a corrosive environment? A: Inconel 625 and Hastelloy C276 bolts do offer similar corrosion resistance but Hastelloy C276 has a slight edge in many acidic environements, especially … Continue reading →

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Alloy 20 fasteners for sulfuric acid corrosion

Posted on August 23, 2017 by dean

Q: I’m working with boiling sulfuric acid and tried Alloy 20 for some of my bolting but am having corrosion. I’m confused as I thought that is what they are best for. Any suggestions. A: You are right Alloy 20 does typically perform very well in sulfuric acid and even … Continue reading →

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Most Common of Hastelloy Fasteners Reviewed

Posted on July 25, 2017 by dean

hastelloy-grades_smallHastelloy alloys have long been the gold standard of corrosion resistant bolts; only out performed by metals like Zirconium and Tantalum. This family of high performance nickel alloys can handle strong acids like hydrochloric, sulfuric, acetic, formic and phosphoric acids, yet each grade actually exhibits its own strengths in dealing with specific acids and niche environments. … Continue reading →

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Hastelloy C276 bolts in hot sulfuric acid

Posted on July 12, 2017 by dean

Inline image 1Q: I was planning on using Hastelloy C276 in hot sulfuric acid. It would be approximately 50% concentration around 100F +/- 10 degrees. Will this be okay? I’m just concerned because I read that it cannot handle strong oxidizing environments and I’ll be using it in an application where its … Continue reading →

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Screws for high velocity salt water with debris

Posted on July 10, 2017 by dean

Q: I have a salt water environment with high velocities and a lot of debris including sand, dirt and particles. Because of the amount of debris, I’m concerned about what material would work best. A: Both Monel and Titanium can be good choices in this situation. Both perform extremely well … Continue reading →

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AL6XN vs Alloy 20 Fasteners: What’s the difference? Which is best?

Posted on June 1, 2017 by dean

These two alloys are often confused as being almost the same, which is almost true. They are both nickel alloys and share many key characteristics. AL6XN and Alloy 20 are alike in that they each retain their strength to about 1000°F. In addition they both perform well, in salt water environments, … Continue reading →

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Zirconium fasteners exposed to downstream oxidizers

Posted on May 25, 2017 by dean

Q: I’m using zirconium fasteners in a sulfuric acid process but they are showing corrosion. I’m not sure why as I’m well below boiling and only using 40% concentration. There may be some downstream contaminants, but not much. Any ideas? A: It is most likely the contaminants that are causing … Continue reading →

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Duplex bolts in sea water contaminated steam turbine

Posted on May 24, 2017 by dean

Q: I’m running a steam surface condenser which is installed on a steam turbine in a thermal power station. I’m using sea water that could be contaminated with chemical pollutants cooling water side of the condenser. Any ideas on a good fastener for the tubes and water boxes? A: Duplex 2205 … Continue reading →

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Best bolts for Inconel 625 flanges

Posted on May 18, 2017 by dean

q: What bolting material should be used with Inconel 625 flanges? We used ASTM A193 Gr B7 however noticing some corrosion issues. A: This is a very common problem but to answer it accurately, it depends on the environment that your flanges see and also to a certain extent what … Continue reading →

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Inconel bolts vs. Monel bolts. What’s the difference? Which is better?

Posted on May 11, 2017 by dean

inconel-monel-chart-copyThey rhyme, are both used in extreme environments, and are both nickel metal alloys, but Monel and Inconel are actually very different. But how? Let’s start with basic chemistry. Monel is a nickel-copper alloy and Inconel is a nickel-chromium alloy. So what does that mean for your extreme application? We … Continue reading →

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Titanium vs Monel: Bolts for stagnant sea water

Posted on April 7, 2017 by dean

Q: I have a seawater application where the water can be stagnant or polluted. Is Monel bolts the best choice? A: For stagnant seawater application we would usually suggest Titanium over Monel fasteners. Although Monel is very resistant to saltwater, it can experience pitting corrosion in stagnant water situations. There have … Continue reading →

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Galvanic corrosion using Inconel bolts

Posted on February 8, 2017 by dean

Q: Can dissimilar (also called galvanic) corrosion occurs between Inconel bolts and regular carbon steel? A:   Anytime you have dissimilar materials you have the potential for galvanic corrosion.  For this to happen the materials need to be wet or in some kind of solution. If they are dry it’s … Continue reading →

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Fasteners for Sulfuric Acid (H2SO4)

Posted on November 11, 2015 by dean

Corrosion Resistant FastenersSulfuric Acid (H2SO4) is one of the most widely used and industrially important acids in modern society, being an essential component in the production of polymers, fuels, pharmaceuticals,  electronics, and mining. While sulfuric acid is commonly used, enabling fasteners to survive in this environment is not always an easy task. To help you tackle this feat, … Continue reading →

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