--- title: Fighting mechanical joint corrosion in saltwater marine environments description: Mechanical joint corrosion in saltwater marine environments is fought by combining three defences image: https://blog.katoadvanex.com/hubfs/marine%20corrosion%20environment.jpg --- [Skip to content](https://blog.katoadvanex.com/fighting-mechanical-joint-corrosion-in-saltwater-marine-environments#main) - [Products](https://www.katoadvanex.com/products/) - [![](https://www.katoadvanex.com/wp-content/uploads/2023/08/tanged-thumbnail.jpg) KATO® Tanged Inserts](https://www.katoadvanex.com/tanged-inserts/) - [![](https://www.katoadvanex.com/wp-content/uploads/2023/08/tangless-thumbnail.jpg) KATO Tangless® Inserts](https://www.katoadvanex.com/tangless-inserts/) - [![](https://www.katoadvanex.com/wp-content/uploads/2023/08/tooling-thumbnail.jpg) KATO® Tooling](https://www.katoadvanex.com/tooling/) - [See all products](https://www.katoadvanex.com/products/) - [Industries](https://www.katoadvanex.com/industries/) - [![](https://www.katoadvanex.com/wp-content/uploads/2023/04/Rectangle-197.png) Aerospace](https://www.katoadvanex.com/aerospace/) - [![](https://www.katoadvanex.com/wp-content/uploads/2023/04/Mask-group-min.webp) Automotive](https://www.katoadvanex.com/automotive/) - [![](https://www.katoadvanex.com/wp-content/uploads/2023/04/electronics-image-semiconductor-1.jpeg) Electronics](https://www.katoadvanex.com/electronics/) - [![](https://www.katoadvanex.com/wp-content/uploads/2023/04/advanex-industry-train.jpg) Rail](https://www.katoadvanex.com/railway/) - [Technology](https://www.katoadvanex.com/kato-technology/) - [Distributors](https://www.katoadvanex.com/distributors/) - [Resources](https://blog.katoadvanex.com/) - [Get Pricing](https://www.katoadvanex.com/contact-us/) [Get Pricing](https://www.katoadvanex.com/contact-us/) Article # Fighting mechanical joint corrosion in saltwater marine environments Posted by Advanex  |   12 November, 2026 Mechanical joint corrosion in saltwater marine environments is fought by combining three defences: materials that resist chloride attack, joint designs that keep seawater out of crevices and away from dissimilar metal contacts, and protection systems such as coatings and cathodic protection. Getting these right at the design stage keeps ship and offshore joints strong and serviceable for decades. ## Why is saltwater so damaging to mechanical joints? Saltwater is damaging because dissolved chlorides turn seawater into a highly conductive electrolyte that breaks down the protective oxide films metals rely on. As TWI explains in its overview of [corrosion and fatigue at sea](https://www.twi-global.com/technical-knowledge/job-knowledge/war-at-sea-the-battle-against-corrosion-and-fatigue-144), oxygen starts the corrosion process while chloride greatly accelerates it, which is why corrosion is far more serious in seawater than in air. Threads and washers also create crevices where seawater stagnates. ## Which areas of ships and offshore structures corrode fastest? The splash zone, the band around the waterline that is repeatedly wetted and dried, typically suffers the highest corrosion rates on offshore structures. Alternating submergence and aeration supplies oxygen and salt, while evaporation concentrates chlorides. Fully immersed steel is comparatively simple to protect with cathodic protection, as summarised in [ScienceDirect's engineering overview of the splash zone](https://www.sciencedirect.com/topics/engineering/splash-zone). | **Marine zone** | **Typical locations** | **Main joint corrosion risk** | | --- | --- | --- | | Atmospheric | Topsides, deck equipment, superstructures | Salt spray; chloride build-up on sheltered surfaces | | Splash | Risers, jacket legs, hull at the waterline | Highest corrosion rates; coatings damaged by wave impact | | Tidal | Piles, quaysides, mooring structures | Wet-dry cycling and differential aeration | | Submerged | Hull bottoms, subsea structures, seawater systems | Crevice corrosion, biofouling and reliance on cathodic protection | ## Which types of corrosion attack marine joints? Crevice, galvanic, pitting and fretting corrosion are the main threats to mechanical joints in saltwater: - **Crevice corrosion**: attack inside threads and under washers, where trapped seawater loses oxygen. - **Galvanic corrosion**: attack on the less noble of two coupled metals. - **Pitting corrosion**: deep, localised chloride attack with little visible surface loss. - **Fretting corrosion**: damage from vibration-driven micro-movement between joint surfaces. ## Is 316 stainless steel enough to stop marine corrosion? “Marine-grade” 316 stainless steel resists saltwater far better than most common grades thanks to its 2–3% molybdenum content, but it is not immune to crevice corrosion in stagnant seawater. The Nickel Institute’s guidance on [austenitic stainless steels in seawater](https://www.nickelinstitute.org/media/8da1c62763103e5/ni-inco_1259-the-successful-use-of-austenitic-stainless-steels-in-seawater.pdf) warns that average corrosion rates are misleading for stainless steels, because attack concentrates in crevices and under deposits such as marine growth. Its test data showed 316 free of pitting in flowing seawater but deeply attacked in still water. Joint geometry therefore matters as much as alloy choice, and super duplex or super austenitic grades are often specified for permanently submerged service. ## How can engineers design joints to resist saltwater corrosion? Engineers resist saltwater corrosion by designing out crevices and dissimilar-metal contact, selecting compatible materials, and protecting what remains with coatings and cathodic protection. That means choosing fastener and thread materials close to the parent metal in the galvanic series, isolating dissimilar metals with non-conductive washers or sleeves, and sealing joints against water ingress. The UK National Physical Laboratory’s [guide to bimetallic corrosion](https://eprintspublications.npl.co.uk/8617/1/Corrosion%20Guide%20No.5.pdf) also stresses area ratio: a small anode coupled to a large cathode intensifies attack. For immersed structures, sacrificial aluminium, zinc or magnesium anodes remain the main defence, and TWI reports that thermally sprayed aluminium coatings can last up to 50 years at sea with minimal maintenance. ## Why does marine joint corrosion matter for lifetime cost? Corroded joints are costly because they drive inspection, repair and replacement in hard-to-reach locations. NACE’s IMPACT study put the global cost of corrosion at US$2.5 trillion a year, and TWI notes that best-practice protection could cut this by up to a third. Seawater also shortens fatigue life: design codes BS EN ISO 19902 and DNV RP-C203 apply a reduction factor of three for free corrosion in seawater, so fatigue design life is a third of that in air. ## How do wire thread inserts protect threaded joints at sea? Wire thread inserts protect marine joints by replacing a weak, corrosion-prone tapped thread with a hard-wearing thread made from a corrosion-resistant alloy. In aluminium hulls and offshore enclosures, a thread tapped into the parent metal is both the load-bearing surface and the part most exposed to attack. An insert in stainless steel or phosphor bronze, a copper alloy well suited to saltwater, gives the fastener a durable thread, spreads load evenly and helps hold clamp load under vibration. Inserts can also be replaced in service rather than scrapping the component.  ## Building durability into marine joints Saltwater finds the weakest point in an assembly, often a threaded joint. Combining the right materials with crevice-free design and proven protection systems keeps marine joints strong for their full design life. KATO Advanex supports manufacturers across marine, aerospace, automotive and electronics with wire thread inserts engineered for corrosive environments. Download our guide below to find out more.  [![Guide: Designing Against Mechanical Joint Failure Transform your approach to mechanical joint design with this expert-written guide. Get the guide](https://hubspot-no-cache-eu1-prod.s3.amazonaws.com/cta/default/27133590/3a0e60e1-f204-4c84-bef3-50a26a99870e.png)](https://hubspot-cta-redirect-eu1-prod.s3.amazonaws.com/cta/redirect/27133590/3a0e60e1-f204-4c84-bef3-50a26a99870e) ### Related Resources from Advanex [View all](https://blog.katoadvanex.com) ### Decades of knowledge. Just try us. Got a question? Want to discuss your requirements? Get in touch with our expert team. [Get in touch](https://www.katoadvanex.com/contact-us/) ### Industries - [Aerospace](https://www.katoadvanex.com/aerospace/) - [Automotive](https://www.katoadvanex.com/automotive/) - [Electronics](https://www.katoadvanex.com/electronics/) - [Rail](https://www.katoadvanex.com/railway/) ### About us - [Our Industries](https://www.katoadvanex.com/industries/) - [Our Technology](https://www.katoadvanex.com/kato-technology/) - [Privacy Policy](https://www.katoadvanex.com/privacy-policy/) - [Data Protection Policy](https://www.katoadvanex.com/data-protection-policy/) ### Products - [Tanged Inserts](https://www.katoadvanex.com/tanged-inserts/) - [Tangless® Inserts](https://www.katoadvanex.com/tangless-inserts/) - [KATO® Tooling](https://www.katoadvanex.com/tooling/) All the latest news and information from KATO [Privacy policy](https://www.katoadvanex.com/privacy-policy/) #### Proud members of: ![IST](https://blog.katoadvanex.com/hubfs/ist.png) ![SMMT](https://blog.katoadvanex.com/hubfs/smmt.png) ![Nottingham Manufacturing Network](https://blog.katoadvanex.com/hubfs/nmn.png) © 2026 Advanex KATO® KATO® Tanged & Tangless® Wire Thread Inserts are manufactured by Advanex Worldwide [Website by Forge®](https://www.forge.uk/) ```json { "@context" : "https://schema.org", "@type" : "BlogPosting", "author" : { "@type" : "Person", "name" : "Advanex", "url" : "https://blog.katoadvanex.com/author/advanex" }, "dateModified" : "2026-11-12T15:25:20.514Z", "datePublished" : "2026-11-12T15:25:20.000Z", "headline" : "Fighting mechanical joint corrosion in saltwater marine environments", "image" : [ "https://blog.katoadvanex.com/hubfs/marine%20corrosion%20environment.jpg" ], "mainEntityOfPage" : { "@id" : "https://blog.katoadvanex.com/fighting-mechanical-joint-corrosion-in-saltwater-marine-environments", "@type" : "WebPage" }, "publisher" : { "@type" : "Organization", "logo" : { "@type" : "ImageObject", "url" : "https://blog.katoadvanex.com/hubfs/kato-advanex-favicon.png" }, "name" : "Advanex Europe Limited" } } ```