If you’re reading this, chances are you work with small-to-medium metal components—maybe you’re a machinist, a product designer, or another supplier who’s struggled with getting a durable, consistent finish on 65mm (2.5 inch) metal parts. For years, I was right there with you. As someone who’s spent the last 12 years running a 65mm metal component supply business, I’ve seen first-hand how many vendors treat these small parts like an afterthought. You might rush through sanding, skip critical preparation steps, and end up with parts that chip, rust, or look dull within months. I once had a client who returned 200 65mm steel brackets because their paint peeled after just three months of outdoor use—and it was all because we cut corners during the painting process. That mistake taught me that painting a 65mm metal surface isn’t just about applying a coat of color; it’s about a sequence of science-backed steps tailored to the part’s size, material, and intended use. Today, I’m breaking down exactly how we paint our 65mm components to a finish that’s stood up to everything from marine equipment to residential kitchen fixtures. Let’s dive in. 65mm (2.5 INCH)
First, a critical note: 65mm is a specific, small size that often gets overlooked. It’s not a large steel beam where you can sand with a power sander and call it a day, nor is it a tiny screw where precision is secondary. A 65mm part—say, a threaded brass bushing, a stamped aluminum bracket, or a cold-rolled steel adapter—has enough surface area to require attention to detail, but not so much that you can ignore small imperfections. When we source metal for our 65mm components, we start by specifying the base material based on the client’s use case, but regardless of metal type, preparation is non-negotiable. You can’t just pull a raw 65mm metal part off the shelf, wipe it down, and paint it. Even parts that look “clean” straight from manufacturing have invisible contaminants that will ruin your finish.
The first step in our process is degreasing. Raw metal comes from the factory with a range of oils, cutting fluids, and protective coatings left over from machining or stamping. These oils create a barrier between the paint and the metal, leading to peeling, blistering, or uneven adhesion. For 65mm parts, we use a two-part degreasing solution: a heavy-duty alkaline cleaner for initial cleaning, followed by a rinse with deionized water to remove all residue. Why deionized water? Tap water has minerals like calcium and magnesium that can leave spots on small, smooth metal surfaces, which are impossible to sand out without damaging the part. We submerge the 65mm parts in the degreaser for 10 minutes at 120°F (49°C)—warm enough to break down oil without warping the small components—then agitate them gently with a soft nylon brush for any crevices, like threaded holes on our adapter parts. After rinsing, we do a “fingerprint test”: if your finger leaves a smudge on the metal, it’s still oily and needs another pass. I learned this trick the hard way when a batch of 65mm aluminum latches came back smudged after painting—we skipped the extra rinse and lost three days of work redoing the whole lot.
Next, we address surface oxidation and roughness with a process called pretreatment, specifically tailored to the metal type of our 65mm parts. If you’re working with steel, oxidation (rust) starts forming on raw metal within hours of exposure to air, so we use a phosphate conversion coating. For aluminum and brass, we use a chromate conversion coating—though I should note that modern, low-VOC (volatile organic compound) formulas are just as effective as the old chromate ones, with less environmental impact. Here’s why this step matters for small 65mm parts: the phosphate or chromate coating etches tiny, microscopic pits into the metal surface, giving the paint something to grip onto. On smooth 65mm steel pins, for example, without this coating, the paint is just sitting on a slick surface, and even a light scratch will take the whole coat off. We submerge our parts in the conversion coating for 5 minutes, then rinse again with deionized water, and let them air-dry in a dust-free chamber. We never towel-dry metal parts, because a paper towel can leave lint that gets trapped under the paint. For clients who want a matte or textured finish, we add a light sandblasting step after degreasing, using 80-grit aluminum oxide blasting media at low pressure—high pressure can warp small 65mm parts, which is a risk we can’t take. We once sandblasted a batch of 65mm zinc-plated steel brackets too hard, and half of them had distorted edges that made them unusable. That’s why low pressure and soft media are key for small components.
Now we move to the primer step, and this is where I see a lot of people go wrong with painting metal parts, especially small ones. Primer isn’t just for adding color; it’s a barrier between the metal and the topcoat, and it fills in tiny imperfections on the surface. For 65mm parts, we use a rust-inhibitive epoxy primer for steel, and an acrylic primer for aluminum and brass. We apply primer using an HVLP (high-volume, low-pressure) spray gun, set to a pressure of 25 PSI—much lower than the 40 PSI many DIYers use. Why? High pressure can blow the tiny 65mm parts around the spray booth, leading to uneven coverage and even scratches if they hit each other. Our parts are held in custom plastic racks during spraying, designed specifically for 65mm components, so they don’t touch each other as the primer dries. We apply a single, thin coat of primer—too thick, and it will drip or crack as it cures. Wait times are critical here: we let the primer cure for 24 hours at 70°F (21°C) and 50% humidity. If it’s too humid, the primer will “blush” (turn cloudy); too dry, and it will cure too fast, leading to poor adhesion. I always tell new clients: don’t rush the primer cure. One year, we had a client ask for a 2-day rush on 500 65mm steel bushing, and we skipped the full cure time to get them done. Within a month, 10% of the parts had primer flaking, and we had to replace them for free. That’s a cost you don’t want to absorb, so patience here pays off.
Once the primer is fully cured, it’s time for the sanding step that makes the finish smooth and even—another step that’s often skipped on small metal parts. For 65mm components, we use 220-grit wet sandpaper to lightly sand the primer surface. Wet sanding is better than dry sanding here because it reduces dust, which is a big risk when working with small parts. We dip the sandpaper in a bucket of deionized water, then gently buff the primer surface in a circular motion, just enough to smooth out any runs or tiny imperfections left from spraying. We don’t sand all the way through the primer—we just want a flat surface so the topcoat looks uniform. After sanding, we rinse the parts again with deionized water and blow them dry with compressed air (set to low pressure, to avoid warping) before moving on to the topcoat. I know this step seems tedious, but it makes the difference between a finish that looks like it was done in a garage and one that looks professional enough for commercial use.
Now, the topcoat selection is the final critical step, and it depends entirely on how your 65mm part will be used. For indoor parts, like decorative metal brackets for furniture, we use a durable acrylic enamel topcoat—it’s affordable, easy to apply, and comes in a wide range of colors. For outdoor parts, like 65mm aluminum hinges for gate hardware, we switch to a polyurethane topcoat, which is resistant to UV rays, rain, and temperature changes. We also offer powder coating for clients who want an extra-durable finish, though powder coating does require more specialized equipment, which is why we only offer it for bulk orders of 100+ parts. When applying the topcoat, we use the same HVLP spray gun setup as primer, keeping the pressure low so the small parts don’t move. We apply two thin coats of topcoat, waiting 1 hour between each coat. After the final coat, we let the parts cure for 7 days at room temperature before packaging. This full cure time allows the topcoat to harden completely, so it doesn’t scratch or smudge during shipping or installation.
Packaging is often an afterthought when painting metal parts, but for 65mm components, it’s just as important as the painting process. These small parts can get scratched or chipped if they’re jostled in packaging, especially if they have sharp edges or threaded holes. We package each batch of 65mm parts in individual plastic bags with foam inserts, separated by cardboard dividers, so they don’t rub against each other. For bulk orders, we add a layer of bubble wrap on top and bottom of the box to cushion them during transit. We’ve had clients receive parts that looked perfect when they left our facility, only to have the finish scratched during shipping—so this final step is non-negotiable.
Over the years, we’ve refined this process specifically for 65mm metal parts, and it’s what sets our supply business apart from others who treat these small components as an afterthought. Whether you need 50 custom 65mm brass pins for a lighting fixture or 1,000 65mm steel brackets for construction, our painting process ensures your parts will hold up to whatever they’re used for, indoors or out. If you’re a designer, contractor, or another business owner who’s tired of dealing with painted metal parts that don’t last, we’d love to hear from you to discuss your specific needs. Just reach out to our team to start a conversation about your next order, and we’ll make sure your 65mm components are painted to the highest standard.
Cast Iron Caster References
- American Society for Metals. (2008). Surface Preparation and Coating of Metals. ASM International.
- ASTM International. (2017). Standard Practice for Applying Organic Coatings by Spraying. ASTM D16-17.
- Metal Finishing Suppliers Association. (2020). Guide to Pretreatment of Small Metal Components for Painting. MFSA Publications.
- Kutz, M. (Ed.). (2019). Handbook of Materials Selection. Wiley.
Chang Chuan Enterprise Co., Ltd.
Chang Chuan Enterprise Co., Ltd. is known as one of the most professional 65mm (2.5 inch) manufacturers and suppliers in Taiwan, China. We warmly welcome you to buy high quality 65mm (2.5 inch) at competitive price from our factory. For customized service, contact us now.
Address: No.93, Chang-an Lane, Antung Village, Hsiu Shui Hsiang, Changhua Hsien, Taiwan
E-mail: cce@ccecasters.com
WebSite: https://www.ccecastors.com/
