Blue vs Red Threadlocker: Complete Guide (Colors, Brands & Codes)
Threadlocker color codes plus the exact product numbers for Loctite, Permatex, Vibra-Tite and 3M — when to use blue, red, purple or green, how to apply it, and how to remove red.
<h2>What Is Threadlocker?</h2><p>Threadlocker is a single-component <strong>anaerobic adhesive</strong>: it stays liquid in the bottle (where there's air) and only cures to a solid once it's trapped between metal threads, away from oxygen. Cured threadlocker fills the microscopic gaps between the male and female threads, which does two jobs at once — it <em>stops the fastener vibrating loose</em> and it <em>seals the threads</em> against moisture and corrosion. Think of it as the chemical alternative to mechanical locking devices like split washers, nylon-insert (nyloc) nuts, and safety wire.</p><p>Threadlockers are sold by <strong>strength grade</strong>, and the industry uses a rough <strong>color code</strong> so you can tell them apart at a glance. Get the grade wrong and you'll either strip or snap the bolt trying to remove it (too strong), or watch it rattle loose on the road (too weak).</p>
<h2>The Threadlocker Color Code</h2><p>Color is the fastest way to read strength — but it's a <em>convention</em>, not a guarantee. The major brands mostly follow it, yet product numbers and exact properties vary by size and region, so always confirm the strength on the label or technical datasheet before you commit.</p><table class="table-auto w-full mb-6"><thead><tr><th class="border px-4 py-2">Color</th><th class="border px-4 py-2">Strength</th><th class="border px-4 py-2">Best for</th><th class="border px-4 py-2">Removal</th></tr></thead><tbody><tr><td class="border px-4 py-2">Purple</td><td class="border px-4 py-2">Low</td><td class="border px-4 py-2">Small screws under 1/4": set screws, carburetor/adjuster screws, electronics</td><td class="border px-4 py-2">Hand tools</td></tr><tr><td class="border px-4 py-2">Blue</td><td class="border px-4 py-2">Medium</td><td class="border px-4 py-2">Most 1/4"–3/4" service fasteners: brake caliper bolts, valve covers, sensors, brackets</td><td class="border px-4 py-2">Hand tools</td></tr><tr><td class="border px-4 py-2">Red</td><td class="border px-4 py-2">High</td><td class="border px-4 py-2">Near-permanent: studs, frame bolts, axle & suspension hardware that should never move</td><td class="border px-4 py-2">Localized heat (~500°F / 260°C), then hand tools</td></tr><tr><td class="border px-4 py-2">Green</td><td class="border px-4 py-2">Wicking / penetrating</td><td class="border px-4 py-2">Fasteners that are <em>already assembled</em> — capillary action wicks it into the threads</td><td class="border px-4 py-2">Hand tools or heat (depends on grade)</td></tr></tbody></table>
<h2>Loctite Threadlocker Codes (Full Lineup)</h2><p>Loctite (made by Henkel) is the original and most widely specified brand. Product numbers often carry a suffix for package size (for example, <em>24221</em> is just 242 in a 10 ml bottle), but the base 3- or 4-digit number tells you the grade.</p><table class="table-auto w-full mb-6"><thead><tr><th class="border px-4 py-2">Grade / Color</th><th class="border px-4 py-2">Product</th><th class="border px-4 py-2">Notes & temperature range</th></tr></thead><tbody><tr><td class="border px-4 py-2">Purple — Low</td><td class="border px-4 py-2">222</td><td class="border px-4 py-2">Small screws under 1/4"; −65 to 300°F; hand-tool removable</td></tr><tr><td class="border px-4 py-2">Blue — Medium</td><td class="border px-4 py-2">242</td><td class="border px-4 py-2">The classic removable grade for 1/4"–3/4" bolts; to 300°F</td></tr><tr><td class="border px-4 py-2">Blue — Medium</td><td class="border px-4 py-2">243</td><td class="border px-4 py-2">242 upgrade — oil-tolerant & primerless; to 360°F</td></tr><tr><td class="border px-4 py-2">Blue — Medium (stick)</td><td class="border px-4 py-2">248</td><td class="border px-4 py-2">Semisolid stick — no drip, great overhead / hard-to-reach</td></tr><tr><td class="border px-4 py-2">Blue — Medium (high-temp)</td><td class="border px-4 py-2">246</td><td class="border px-4 py-2">Heat resistant to 450°F</td></tr><tr><td class="border px-4 py-2">Blue — Medium (ultra-high-temp)</td><td class="border px-4 py-2">2422</td><td class="border px-4 py-2">To 650°F</td></tr><tr><td class="border px-4 py-2">Red — High</td><td class="border px-4 py-2">271</td><td class="border px-4 py-2">High-strength workhorse for permanent assembly</td></tr><tr><td class="border px-4 py-2">Red — High</td><td class="border px-4 py-2">263</td><td class="border px-4 py-2">Oil-tolerant & primerless; to 360°F</td></tr><tr><td class="border px-4 py-2">Red — High (high-temp)</td><td class="border px-4 py-2">272</td><td class="border px-4 py-2">Heat resistant to 450°F</td></tr><tr><td class="border px-4 py-2">Red — High (large bolts)</td><td class="border px-4 py-2">277</td><td class="border px-4 py-2">For bolts roughly 1" and larger</td></tr><tr><td class="border px-4 py-2">Red — High (stick)</td><td class="border px-4 py-2">268</td><td class="border px-4 py-2">Semisolid stick, high strength</td></tr><tr><td class="border px-4 py-2">Red — High (ultra-high-temp)</td><td class="border px-4 py-2">2620</td><td class="border px-4 py-2">To 650°F</td></tr><tr><td class="border px-4 py-2">Green — Wicking</td><td class="border px-4 py-2">290</td><td class="border px-4 py-2">Penetrates pre-assembled fasteners; medium-to-high hold</td></tr></tbody></table>
<h2>Permatex Threadlocker Codes</h2><p>Permatex is the threadlocker you'll most often find on auto-parts-store shelves. Same color logic as Loctite.</p><table class="table-auto w-full mb-6"><thead><tr><th class="border px-4 py-2">Grade / Color</th><th class="border px-4 py-2">Part numbers</th><th class="border px-4 py-2">Use</th></tr></thead><tbody><tr><td class="border px-4 py-2">Purple — Low</td><td class="border px-4 py-2">24024</td><td class="border px-4 py-2">Small fasteners under 1/4"</td></tr><tr><td class="border px-4 py-2">Blue — Medium</td><td class="border px-4 py-2">24200 (liquid), 24010 (gel), 24206 / 24210 / 24240</td><td class="border px-4 py-2">The everyday removable pick</td></tr><tr><td class="border px-4 py-2">Red — High</td><td class="border px-4 py-2">27100, 27110, 27140, 27150</td><td class="border px-4 py-2">Permanent assembly</td></tr><tr><td class="border px-4 py-2">Red — High (high-temp)</td><td class="border px-4 py-2">27200, 27240</td><td class="border px-4 py-2">Heat-resistant permanent</td></tr><tr><td class="border px-4 py-2">Green — Wicking</td><td class="border px-4 py-2">29000, 29040</td><td class="border px-4 py-2">Penetrating, applied after assembly</td></tr></tbody></table>
<h2>Vibra-Tite & 3M Threadlocker Codes</h2><p>Two more brands common in industrial and OEM work:</p><table class="table-auto w-full mb-6"><thead><tr><th class="border px-4 py-2">Vibra-Tite</th><th class="border px-4 py-2">Grade / Color</th></tr></thead><tbody><tr><td class="border px-4 py-2">111</td><td class="border px-4 py-2">Low (purple)</td></tr><tr><td class="border px-4 py-2">121</td><td class="border px-4 py-2">Medium (blue)</td></tr><tr><td class="border px-4 py-2">131</td><td class="border px-4 py-2">High (red)</td></tr><tr><td class="border px-4 py-2">137 / 140</td><td class="border px-4 py-2">High strength / high-temp (red)</td></tr><tr><td class="border px-4 py-2">150</td><td class="border px-4 py-2">Wicking (green)</td></tr><tr><td class="border px-4 py-2">VC-3 Threadmate</td><td class="border px-4 py-2">Repositionable — a flexible coating you can remove and re-fasten many times</td></tr></tbody></table><table class="table-auto w-full mb-6"><thead><tr><th class="border px-4 py-2">3M Scotch-Weld</th><th class="border px-4 py-2">Grade / Color</th></tr></thead><tbody><tr><td class="border px-4 py-2">TL22</td><td class="border px-4 py-2">Low (purple)</td></tr><tr><td class="border px-4 py-2">TL42 / TL43</td><td class="border px-4 py-2">Medium (blue)</td></tr><tr><td class="border px-4 py-2">TL62 / TL71 / TL72 / TL77 / TL90</td><td class="border px-4 py-2">High (red) and wicking grades</td></tr></tbody></table>
<h2>Blue vs Red: Which One Do You Actually Need?</h2><p>This is the decision that trips up most DIYers. The rule of thumb: <strong>Blue if you'll ever take it apart again; Red if it should never move.</strong></p><table class="table-auto w-full mb-6"><thead><tr><th class="border px-4 py-2">Question</th><th class="border px-4 py-2">Blue (medium)</th><th class="border px-4 py-2">Red (high)</th></tr></thead><tbody><tr><td class="border px-4 py-2">Will you service this part?</td><td class="border px-4 py-2">Yes — caliper bolts, valve covers, sensors, brackets</td><td class="border px-4 py-2">No — studs, frame/subframe bolts, bellhousing</td></tr><tr><td class="border px-4 py-2">Vibration / load</td><td class="border px-4 py-2">Normal</td><td class="border px-4 py-2">Severe or structural</td></tr><tr><td class="border px-4 py-2">How you'll remove it</td><td class="border px-4 py-2">Hand tools</td><td class="border px-4 py-2">Heat to ~500°F first, then hand tools</td></tr></tbody></table><p>When in doubt on a serviceable part, choose blue. Red on a bolt you later need to remove cold is exactly how threads get stripped and bolt heads snap off.</p>
<h2>Green (Wicking) Threadlocker — The One Most People Miss</h2><p>Wicking grade (Loctite 290, Permatex 29000) is <em>thin</em> and built to be applied to fasteners that are <strong>already assembled and torqued</strong>. Capillary action draws it down into the engaged threads. It's perfect for locking a bolt you discovered was loose without tearing the assembly apart — set screws, electrical terminals, and pre-set adjustments.</p>
<h2>How to Apply Threadlocker the Right Way</h2><p>Threadlocker only works on clean, dry threads, and it changes how a fastener torques. Follow these steps:</p><p><img src="https://wmnmphhnejxoqlradebf.supabase.co/storage/v1/object/public/bolt-images/apply_blue_threadlocker.png" alt="Applying blue medium-strength threadlocker to clean steel bolt threads" style="width:100%;max-width:720px;height:auto;border-radius:8px" /></p><table class="table-auto w-full mb-6"><thead><tr><th class="border px-4 py-2">Step</th><th class="border px-4 py-2">What to do</th></tr></thead><tbody><tr><td class="border px-4 py-2">1. Clean</td><td class="border px-4 py-2">Degrease the bolt and the hole with brake cleaner; remove old cured threadlocker, oil, and debris. Anaerobics hate contamination.</td></tr><tr><td class="border px-4 py-2">2. Dry</td><td class="border px-4 py-2">Let the threads dry fully. For oily or blind holes, use an oil-tolerant grade (Loctite 243 / 263) or a primer.</td></tr><tr><td class="border px-4 py-2">3. Apply</td><td class="border px-4 py-2">A few drops on the engaged threads is plenty. In a blind hole, put a little down the hole too. For wicking grade, apply along the thread line after assembly.</td></tr><tr><td class="border px-4 py-2">4. Assemble & torque</td><td class="border px-4 py-2">Tighten to spec. Important: wet threadlocker acts as a lubricant, so use the "wet" torque value if your manual lists one — otherwise you'll over-tension the bolt.</td></tr><tr><td class="border px-4 py-2">5. Cure</td><td class="border px-4 py-2">Hand-tight strength in ~10–20 minutes; full cure in about 24 hours. Don't load it hard until it's cured.</td></tr></tbody></table>
<h2>How to Remove Red (High-Strength) Threadlocker</h2><p>Red is designed to be permanent, so don't just crank harder — you'll snap the bolt. Apply <strong>localized heat</strong> with a heat gun or torch until the fastener reaches roughly <strong>500°F (260°C)</strong>; the adhesive softens and breaks down, and the bolt backs out while it's still warm. Work safely: heat-resistant gloves, eye protection, and keep flame well away from fuel lines, plastics, and rubber.</p><p><img src="https://wmnmphhnejxoqlradebf.supabase.co/storage/v1/object/public/bolt-images/red_threadlocker.png" alt="Red high-strength threadlocker on stud threads, which requires heat to remove" style="width:100%;max-width:720px;height:auto;border-radius:8px" /></p>
<h2>Common Threadlocker Mistakes</h2><table class="table-auto w-full mb-6"><thead><tr><th class="border px-4 py-2">Mistake</th><th class="border px-4 py-2">Why it bites you</th></tr></thead><tbody><tr><td class="border px-4 py-2">Using red where blue belongs</td><td class="border px-4 py-2">Turns a 5-minute job into a torch-and-pray removal — or a snapped bolt</td></tr><tr><td class="border px-4 py-2">Applying to dirty/oily threads</td><td class="border px-4 py-2">The bond won't form. Clean and dry first (or use an oil-tolerant grade)</td></tr><tr><td class="border px-4 py-2">Using it on plastic</td><td class="border px-4 py-2">Anaerobics can craze and crack many plastics — use a plastic-safe product</td></tr><tr><td class="border px-4 py-2">Ignoring the torque change</td><td class="border px-4 py-2">Wet threadlocker lubricates; use wet-torque values or you'll over-tighten</td></tr><tr><td class="border px-4 py-2">Locking critical / TTY fasteners blindly</td><td class="border px-4 py-2">Some torque-to-yield or pre-coated bolts are designed dry — check the service manual</td></tr></tbody></table>
<h2>Threadlocker FAQ</h2><p><strong>Is blue threadlocker permanent?</strong> No — medium-strength blue is removable with ordinary hand tools. That's the whole point. Use red when a fastener should never come loose.</p><p><strong>Can I reuse threadlocker?</strong> Scrape and clean the old cured product off and apply fresh — don't rely on the old bond. The exception is Vibra-Tite VC-3, which is designed to be repositionable.</p><p><strong>Does threadlocker expire?</strong> Yes. Anaerobics have a shelf life (typically around two years unopened, less once opened); old product cures poorly and won't hold.</p><p><strong>Threadlocker or a lock washer?</strong> Threadlocker also seals the joint and works where washers can't; mechanical locks can be reused instantly. Plenty of critical joints use both.</p>
<h2>Recommended Threadlockers</h2><p>Not sure what to grab? These cover almost every job around the garage. <em>WhatSizeBolt is an Amazon Associate — purchases made through these links may earn us a commission at no extra cost to you.</em></p><table class="table-auto w-full mb-6"><thead><tr><th class="border px-4 py-2">Product</th><th class="border px-4 py-2">Best for</th><th class="border px-4 py-2">Link</th></tr></thead><tbody><tr><td class="border px-4 py-2">Loctite 243 (Blue, medium)</td><td class="border px-4 py-2">Everyday serviceable bolts — calipers, brackets, sensors</td><td class="border px-4 py-2"><a href="https://www.amazon.com/s?k=loctite+243+threadlocker&tag=whatsizebol0a-20" target="_blank" rel="nofollow sponsored noopener">View on Amazon</a></td></tr><tr><td class="border px-4 py-2">Loctite 271 (Red, high)</td><td class="border px-4 py-2">Permanent studs, frame & suspension bolts</td><td class="border px-4 py-2"><a href="https://www.amazon.com/s?k=loctite+271+threadlocker&tag=whatsizebol0a-20" target="_blank" rel="nofollow sponsored noopener">View on Amazon</a></td></tr><tr><td class="border px-4 py-2">Loctite 290 (Green, wicking)</td><td class="border px-4 py-2">Locking fasteners that are already assembled</td><td class="border px-4 py-2"><a href="https://www.amazon.com/s?k=loctite+290+wicking+threadlocker&tag=whatsizebol0a-20" target="_blank" rel="nofollow sponsored noopener">View on Amazon</a></td></tr><tr><td class="border px-4 py-2">Loctite 222 (Purple, low)</td><td class="border px-4 py-2">Small screws under 1/4"</td><td class="border px-4 py-2"><a href="https://www.amazon.com/s?k=loctite+222+threadlocker&tag=whatsizebol0a-20" target="_blank" rel="nofollow sponsored noopener">View on Amazon</a></td></tr><tr><td class="border px-4 py-2">Permatex Threadlocker Blue (24200)</td><td class="border px-4 py-2">Budget-friendly medium-strength pick</td><td class="border px-4 py-2"><a href="https://www.amazon.com/s?k=permatex+24200+threadlocker+blue&tag=whatsizebol0a-20" target="_blank" rel="nofollow sponsored noopener">View on Amazon</a></td></tr><tr><td class="border px-4 py-2">Permatex Threadlocker Red (27100)</td><td class="border px-4 py-2">Budget-friendly high-strength pick</td><td class="border px-4 py-2"><a href="https://www.amazon.com/s?k=permatex+27100+threadlocker+red&tag=whatsizebol0a-20" target="_blank" rel="nofollow sponsored noopener">View on Amazon</a></td></tr><tr><td class="border px-4 py-2">Threadlocker assortment (blue + red)</td><td class="border px-4 py-2">Keeping every grade on the shelf</td><td class="border px-4 py-2"><a href="https://www.amazon.com/s?k=threadlocker+assortment+blue+red&tag=whatsizebol0a-20" target="_blank" rel="nofollow sponsored noopener">View on Amazon</a></td></tr></tbody></table>
<p>Know your fastener before you lock it: look up the exact size and torque for your vehicle with our <a href="/vehicles">vehicle-specific torque tool</a>, brush up on <a href="/knowledge-hub/torque-specs">how to read torque specs</a>, and pick the right tool in our <a href="/knowledge-hub/best-torque-wrenches">torque wrench guide</a>.</p>