{"id":612,"date":"2026-10-21T10:25:06","date_gmt":"2026-10-21T02:25:06","guid":{"rendered":"http:\/\/www.albenisi.com\/blog\/?p=612"},"modified":"2026-10-21T10:25:06","modified_gmt":"2026-10-21T02:25:06","slug":"how-to-improve-the-corrosion-resistance-of-cnc-turning-parts-4534-2e355e","status":"publish","type":"post","link":"http:\/\/www.albenisi.com\/blog\/2026\/10\/21\/how-to-improve-the-corrosion-resistance-of-cnc-turning-parts-4534-2e355e\/","title":{"rendered":"How to improve the corrosion resistance of CNC turning parts?"},"content":{"rendered":"

Hey everyone, it\u2019s Jake here \u2013 I run a CNC turning parts shop, and let\u2019s be real: corrosion is the silent killer for the parts we make. I\u2019ve lost count of how many clients have come to me with parts that seized up, rusted through, or failed way earlier than they should\u2019ve, just because someone skipped the right corrosion resistance steps. Most of the time, it\u2019s not that the CNC turning process itself was bad \u2013 it\u2019s the little after-machine steps, material choices, and even how you handle parts after they leave my shop that make all the difference. If you\u2019re someone who relies on CNC turned parts (whether for automotive, industrial machinery, medical devices, whatever), this is the stuff you need to know to keep your parts working for years, not months. CNC Turning Parts<\/a><\/p>\n

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First off, let\u2019s talk basics: why do CNC turned parts corrode in the first place? When we machine metal, we\u2019re cutting into it, which creates tiny surface cracks, residual stress, and even microscopic debris stuck in the tool marks. Those are perfect little spots for moisture, salt, or other corrosive stuff to get in and start eating away. If you\u2019re using carbon steel, that\u2019s especially tricky because it\u2019s naturally prone to rust \u2013 even a little condensation in a warehouse can turn a part that was supposed to last 10 years into a mess in 6 months. Aluminum, on the other hand, forms a protective oxide layer, but if that layer gets scratched during machining or handling, corrosion can start right under it, hidden from view. Stainless steel? Don\u2019t get me started \u2013 people think it\u2019s \u201cstain-less\u201d for good reason, but it still can corrode (that\u2019s what pitting is, basically) if it\u2019s exposed to chlorides like saltwater or even some cleaning chemicals.<\/p>\n

Okay, so let\u2019s get into the actual fixes. I break this down into three main buckets: pick the right material for the job, add a protective coating after machining, and nail the post-machining handling process. None of these work alone, but if you combine them, you\u2019re way ahead of the game.<\/p>\n

First, material selection. This is the foundation, right? You can coat a cheap carbon steel part, but it\u2019ll never perform as well as a properly coated alloy that\u2019s made for corrosion. Let\u2019s go through the most common materials we use for CNC turning and when to pick which:<\/p>\n

Carbon steel: It\u2019s cheap, strong, and easy to machine, but it\u2019s a corrosion sponge. You shouldn\u2019t use this for outdoor parts, parts that go near salt, or parts that sit in damp environments \u2013 not unless you plan on a heavy-duty coating. If you have to use carbon steel (like for a low-stress indoor bracket), go for a low-carbon steel? Wait, no \u2013 actually, medium-carbon steel is better for strength, but if you\u2019re going to coat it, just make sure it\u2019s a grade without too many impurities (like AISI 1018 is way better than some cheaper foreign grades for coating adhesion). Another thing: if you\u2019re working with carbon steel, avoid machining it right after it\u2019s been heat-treated. Heat-treating creates residual stress that can make coatings peel off, so let it cool and stress-relieve first if you can.<\/p>\n

Aluminum: Super popular for aerospace, automotive, and consumer goods because it\u2019s light. The natural oxide layer is good, but it\u2019s thin and can get damaged. For parts that need extra corrosion resistance, go for 6061-T6 instead of 1050 or pure aluminum \u2013 6061 has better strength and the oxide layer forms more evenly, plus it\u2019s way easier to coat. If you\u2019re dealing with marine parts, 5052 aluminum is even better \u2013 it has higher magnesium, which makes the oxide layer more resistant to salt corrosion. That\u2019s a big one for anyone in boat parts or offshore equipment.<\/p>\n

Stainless steel: 304 is the workhorse, 316 is the marine-grade hero. 304 works fine for most indoor stuff, but if you\u2019re near salt or chemicals, 316 is non-negotiable. The molybdenum in 316 creates a layer that resists chloride corrosion way better. Also, don\u2019t machine stainless steel with a cutting tool that\u2019s worn out \u2013 worn tools create rough surface finishes, which are way more likely to trap corrosive agents. Rough surfaces = more crevices for water to sit, so smoother is better here.<\/p>\n

Now, the next big one: coatings. This is where most people cut corners, and it\u2019s the difference between a part that rusts in 6 months and one that lasts 10 years. Not all coatings are created equal, and some work way better with certain materials and environments. Let\u2019s run through the ones we use most at my shop, and when to use each:<\/p>\n

Electroplating: This is the old reliable. Zinc plating is the go-to for carbon steel \u2013 it\u2019s cheap, easy, and acts as a sacrificial layer. That means if the coating gets scratched, the zinc corrodes instead of the steel underneath. Perfect for indoor parts like brackets, hardware, or automotive trim that doesn\u2019t see salt. But wait, if you\u2019re using zinc plating on parts that will be outside, add a chromate conversion coating on top \u2013 it seals the tiny pores in the zinc and makes it way more corrosion-resistant. We use yellow chromate for parts that don\u2019t mind a little color, clear for when you want the metal to show through. For aluminum, we do electroless nickel plating \u2013 it\u2019s way better than electroplating because it deposits evenly, even on the internal threads or complex shapes that CNC turning creates. Electroless nickel is also super hard, so it resists scratching, which is key for aluminum because the oxide layer is easy to damage.<\/p>\n

Anodizing: This is my favorite for aluminum parts. It\u2019s not a \u201ccoating\u201d in the traditional sense \u2013 it grows the oxide layer right into the surface of the aluminum, so it\u2019s way more durable than plating. You can adjust the thickness: thin anodizing (10 microns) for cosmetics, thick anodizing (50+ microns) for outdoor parts or parts that take wear. Clear anodizing for when you want to keep the aluminum\u2019s silver look, black for when you need heat resistance (it absorbs heat better). But wait \u2013 anodizing only works on aluminum, so if you\u2019re dealing with steel or brass, you can\u2019t use it. Also, avoid anodizing parts that have tight tolerances \u2013 the thick anodizing can add a few microns, which might throw off how your part fits. We usually mention that to clients right away, so no surprises.<\/p>\n

Powder coating: This is the big one for heavy-duty corrosion resistance, especially for larger parts or parts that see a lot of outdoor exposure. It\u2019s a dry powder that we electrostatically spray on, then bake, so it forms a thick, hard film that\u2019s way more resistant to scratches and chemicals than wet paint. We use polyester powder coating for most things \u2013 it\u2019s UV-resistant, so it doesn\u2019t fade or peel in sunlight. For industrial parts that deal with chemicals, epoxy powder coating is better \u2013 it\u2019s more resistant to acids and solvents. Just a heads up: powder coating does add thickness, so again, if you have super tight tolerances (like parts that screw together, with 0.001\u201d clearance), you might need to machine the parts a little oversized first to account for the coating. That\u2019s a trick we share with all our clients, so they don\u2019t end up with parts that won\u2019t fit.<\/p>\n

Passivation: This is a must for stainless steel parts, and most people skip it \u2013 that\u2019s a mistake. After machining, stainless steel has tiny amounts of iron and other contaminants on its surface from cutting tools or chips, which will cause it to rust. Passivation uses a mild acid (usually nitric or citric acid) to remove those contaminants and create a pure, protective oxide layer. If you don\u2019t do this, even 316 stainless steel can get spot rust in a few months. We always include passivation for any stainless steel parts we make, but if a client is going to do it themselves later, we make sure to send clear instructions on how to do it right \u2013 no skipping that step.<\/p>\n

Wait, let\u2019s talk about post-machining handling and storage, because this is where even the best materials and coatings go to waste. I\u2019ve had clients bring in parts that look great when they leave my shop, rusted to hell a month later, just because they stored them wrong. Here\u2019s the lowdown:<\/p>\n

First, don\u2019t leave CNC turned parts wrapped in the paper they come with from machining (that oily paper) for longer than a week. The oil is there to protect during transport, but it can trap moisture if it\u2019s left on too long. When parts arrive at your facility, unwrap them, wipe them down with a lint-free cloth (no paper towels \u2013 they leave lint that can hold water), and store them in a dry place. If your warehouse has high humidity (over 50%), get desiccant packets or use a dehumidifier \u2013 even a little extra moisture will speed up corrosion.<\/p>\n

Also, don\u2019t stack parts directly on top of each other if they\u2019re coated. If you have two powder-coated parts rubbing together, they can scratch the coating, which is an entry point for corrosion. Use plastic dividers or place each part in a separate bin. For threaded parts (like bolts or fittings), coat the threads with a light anti-seize compound \u2013 this prevents galling when you assemble them, and also creates a barrier against moisture. I know some people skip anti-seize because it\u2019s an extra step, but it saves you from having parts that seize up when you need them, and it adds another layer against corrosion.<\/p>\n

Another thing: avoid using harsh cleaning chemicals on finished parts. If you need to clean them, use a mild soap and water, or a chemical specifically made for the coating you used. For example, don\u2019t use bleach on powder-coated parts \u2013 it\u2019ll eat through the finish. For stainless steel, use a non-abrasive cleaner to avoid scratching the passivated layer. I\u2019ve seen clients power wash parts with too much pressure, which damages coatings and roughs up surfaces, leading to corrosion.<\/p>\n

Wait, let\u2019s throw in a common mistake we see all the time: people choosing a coating based on cost, not the environment. I once had a client who made agricultural equipment, and he wanted to use zinc plating for parts that go through rain and mud. I told him powder coating would be way better, but he went with zinc because it was 30% cheaper. Six months later, he came back \u2013 half the parts were rusted through, and he had to replace them. That\u2019s not a win for anyone. The up front cost of a better coating is way less than the cost of replacing parts, downtime, and lost productivity.<\/p>\n

Also, for medical or food-grade parts, you have to make sure your coatings are compliant with FDA or EU standards. A lot of cheap electroplating has heavy metals that can leach into food or body fluids, so we only use coatings that are certified for food and medical use. That\u2019s something we vet for all our clients in those industries, so they don\u2019t end up with parts that get rejected for non-compliance.<\/p>\n

Let me wrap this up with a quick checklist, so you guys don\u2019t forget the key points: 1) Match your material to the environment \u2013 carbon steel for indoor, 316 aluminum for marine, etc. 2) Don\u2019t skip passivation for stainless steel, and pick the right coating: zinc for indoor steel, anodizing for aluminum, powder coating for heavy outdoor use. 3) Handle and store parts right \u2013 no leaving them wrapped too long, no stacking coated parts, keep humidity low. 4) Don\u2019t cut corners on cost for coatings \u2013 it\u2019ll bite you later.<\/p>\n

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If you\u2019re working on a project and you\u2019re not sure which combination is right for you, don\u2019t overthink it. We make custom CNC turning parts for all kinds of industries, and we can walk you through every step \u2013 from material selection to coating to post-machining tips. Just hit us up to chat through your needs, and we\u2019ll make sure you get parts that last, not parts that corrode in a few months.<\/p>\n

Five-axis Machining<\/a> References<\/p>\n

    \n
  1. ASM International. (2004). Corrosion: Materials. ASM Handbook, Vol. 13A.<\/li>\n
  2. Askeland, D. R., & Fulay, P. P. (2016). The Science and Engineering of Materials. Cengage Learning.<\/li>\n
  3. National Association of Corrosion Engineers (NACE). (2018). Corrosion Control for Machined Components.<\/li>\n
  4. Aluminum Association. (2020). Anodizing Guidelines for Aluminum Alloys.<\/li>\n
  5. International Organization for Standardization (ISO). (2019). ISO 9223: Corrosion of Metals and Alloys \u2013 Corrosivity of Atmospheres \u2013 Classification.<\/li>\n<\/ol>\n
    \n

    Dongguan Tuoyue Hardware Technology Co., Ltd.<\/a><\/p>\n

    Address: No.2, Lane 7, Industrial Road, Lingtou Village, Qiaotou Town, Dongguan City, Guangdong Province
    E-mail: 346320463@qq.com
    WebSite:     https:\/\/www.toyuehardware.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    Hey everyone, it\u2019s Jake here \u2013 I run a CNC turning parts shop, and let\u2019s be … How to improve the corrosion resistance of CNC turning parts?<\/span>Read more<\/a><\/p>\n","protected":false},"author":342,"featured_media":612,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[575],"class_list":["post-612","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry","tag-cnc-turning-parts-43e6-2ee3fd"],"_links":{"self":[{"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/posts\/612","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/users\/342"}],"replies":[{"embeddable":true,"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/comments?post=612"}],"version-history":[{"count":0,"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/posts\/612\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/posts\/612"}],"wp:attachment":[{"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/media?parent=612"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/categories?post=612"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.albenisi.com\/blog\/wp-json\/wp\/v2\/tags?post=612"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}