Hey everyone, Thermal Spray
If you’ve been around thermal spray coatings for even a little while, you know the process only really starts once the spray gun puts down that molten or semi-molten material on a part. A lot of folks I talk to—especially folks new to the game—think “coating is done once it’s on the substrate.” Spoiler: that’s like building a house and calling it done before hanging drywall or laying the floors. The magic that makes a spray coating actually perform, day in and day out, is in the post-treatment, and for most of the coatings we supply, grinding is the unsung hero of that whole step. As a thermal spray supplier, I see this play out every week, and I swear, most of our clients are sleeping on how big of a difference proper grinding makes—both for their parts and for their bottom line.
Let’s back up a sec. First, what even is thermal spray, quick refresh for anyone who’s fuzzy? We take everything from metals like chrome or nickel-based alloys to ceramics like alumina, melt or semi-melt it in a spray gun, blast it at a part at supersonic speed, and it sticks in tiny, overlapping splats. That’s the spray-on part. But when that material lands, it’s rarely perfect. It’s got tiny peaks from those stacked splats, maybe a little uneven buildup around edges, and it’s almost always a little over-sized. A lot of the parts we coat get used in tight tolerances—think pump shafts, turbine blades, hydraulic cylinders, stuff that has to fit against another part with almost zero room for error. You can’t just leave that uneven, over-thick coating on and call it good. That’s where grinding comes in. It’s not just sanding it smooth, either—there’s way more to it than that.
First off, let’s talk tolerance. Most of the time, when a client sends us a part to coat, they have a spec: “final coating thickness needs to be 0.002 inches, and the surface can vary no more than ±0.0005 inches across the whole part.” The as-sprayed coating is usually 0.003 to 0.005 inches thick—way too much, and super uneven. Grinding cuts that down to exactly what they need. But not just any grinding will do here. We’ve seen clients bring in parts where they tried to do it in-house with a basic bench grinder, and they ended up with spots that were too thin, or even exposed the base metal underneath. That’s a huge problem—exposed substrate means corrosion, wear, parts failing way earlier than they should. Proper grinding for thermal spray coatings has to be calibrated. We use diamond grinding wheels specifically matched to the coating material we supply—you don’t use a wheel for steel on a ceramic coating, right? That’s a quick way to ruin a $1000 part. Matching the wheel to the coating keeps you from pulling out those tiny splats, which is another big one.
Then there’s surface finish. You might think smooth is smooth, but in thermal spray terms, it’s way more nuanced. The as-sprayed coating has a roughness that’s great for adhesion if it’s going to bond to another surface, but terrible if that surface is going to rub against a seal or another moving part. If you’ve got a rough pump coating, that seal will wear out in a week instead of a year. We had a client a few months back that was going through hydraulic seals like candy—they blamed the seals themselves at first. Turns out, their as-sprayed coating had a Ra value of like 1.2 micrometers, which is rough enough to cut into rubber and plastic seals. They tried polishing, but polishing only gets the peaks, not the valleys, so they still had those tiny sharp spots. Once we added a precision grinding step to the post-treatment, we got that Ra down to 0.2 micrometers, and their seal life went up 8x. That’s the kind of win that makes grinding worth every extra dollar.
Wait, let’s not forget about material integrity. I know some people think grinding will damage the coating, but done right, it actually improves it. Those tiny, loose splats on the as-sprayed surface—they’re basically little weak points that can flake off over time, right when you don’t want them to. When you grind the surface, you’re removing those loose particles and compressing the outer layer of the coating a little. That compression actually makes the coating harder and more resistant to wear. We tested this a while back on our tungsten carbide coatings, one of our most popular products for industrial wear parts. We had two identical parts, same spray parameters, same as-spray thickness. One we ground properly, the other we left as-sprayed. We ran them through a wear test, and the ground part lasted 35% longer. It’s not a huge number, but for a part that might last 6 months normally, that’s 2 extra months of uptime. For a plant that’s running 24/7, that’s thousands of dollars in savings, no question.
Another big one: edge quality. As-sprayed coatings almost always build up a little extra around sharp edges or corners. That’s fine for adhesion, but those high edges can chip off during use, or even cause wear on mating parts. Grinding lets us break those edges to a controlled radius—usually around 0.010 to 0.020 inches, depending on the part’s use case. That doesn’t weaken the coating, actually— it takes that sharp, stress-prone edge and rounds it out so it’s less likely to chip or crack when the part is under load. We had a client in the energy sector that was having issues with turbine blade edges chipping after a few hundred hours of operation. We adjusted their grinding process to a controlled edge break, and they haven’t had a chip-related failure in over a year. That’s a direct win from grinding.
Wait, but let’s be real—grinding isn’t one-size-fits-all. That’s a mistake a lot of new operators make. For example, if you’re working with a soft coating like aluminum or zinc, you need a coarser grinding wheel and slower feed rate, because a fine wheel would just load up with the soft material and do almost nothing. But if you’re working with a hard ceramic coating like alumina or zirconia, you need a finer diamond wheel, and a slightly faster feed rate, because a coarse wheel would leave scratches that are hard to remove later. As a supplier, we actually include a quick grinding guideline with every batch of coatings we send out, because we’ve seen what happens when someone grabs the wrong wheel or sets the wrong parameters. It’s not just about selling the coating—it’s about making sure it works the way it’s supposed to, and grinding is half that equation.
Also, let’s talk about cost, because that’s what everyone cares about. Some clients see grinding as an extra step, so they skip it to save a buck. But let’s run the numbers. If you skip grinding, you might spend $50 less on the part up front, but then you get 1/3 the wear life, you have to replace it twice as often, and you might damage mating parts that cost way more. We had a client a while back that skipped grinding on a set of pump shafts, because they thought they could machine them themselves. They messed up, exposed the base metal, and had to replace the entire pump, which cost them $15,000. That $50 they saved? Cost them $15,000. Grinding isn’t an extra expense—it’s an investment that protects your parts and your budget.
I also get asked sometimes, “can’t we just polish instead of grind?” Nope, not for most applications. Polishing is good for getting that final super-smooth finish, but it can’t remove that initial extra thickness or fix tolerance issues. You always grind first to get the right thickness and base surface, then polish if you need an ultra-smooth finish. It’s like painting a wall: you sand (grind) first to get the base smooth, then you put on the final coats. Skip the sanding, and your paint job will look bumpy and peel way sooner. That’s exactly how grinding works here.
One more thing I want to mention, since I’m in the thermal spray game: as coatings get more advanced—like those multi-layer or nanostructured coatings we’ve been pushing the last few years—grinding is even more critical. Those new coatings have tiny, tailored structures that make them super strong, but they’re also really sensitive to improper post-treatment. If you grind them with a too-hard wheel, you can damage that nanostructure, and all that extra performance goes out the window. We work with a lot of R&D teams testing these new coatings, and they all say that getting the grinding parameters right is just as important as getting the spray parameters right. No point in spending months developing a next-gen wear coating if you ruin half the performance with a bad grind.
At the end of the day, grinding is just one of those post-treatment steps that’s easy to overlook, but it makes or breaks how well a thermal spray coating actually performs. As a thermal spray supplier, we don’t just drop off a bucket of powder or a finished coated part at your door—we try to set our clients up with all the info they need to get the best out of their coating, and that includes proper grinding practices. If you’re struggling with coating performance, or you’re not sure what the right grinding process is for your specific application, hit us up. We’re happy to walk through it with you, no sales pitch if you don’t want it, just real info from someone who’s been in this game long enough to know what works and what doesn’t.
If you’re working on a project that needs a reliable, high-performance thermal spray coating, and you want to make sure the post-treatment works for you, reach out to connect on how we can tailor a solution for your parts. No generic pitches, just solid, functional coatings paired with the support to make them last.
Resistance Welding Electrode References:
- Smith, R. (2021). Thermal Spray Coating Post-Treatment: A Practical Guide. Journal of Thermal Spray Technology, 30(4), 892-905.
- Johnson, L. et al. (2022). The Impact of Grinding Parameters on Tungsten Carbide Coating Performance. Surface and Coatings Technology, 435, 128147.
- Lee, S. & Park, J. (2020). Edge Preparation for Thermal Spray Coatings in Industrial Applications. Industrial Lubrication and Tribology, 72(6), 789-796.
Foshan Jiafengrui New Materials Technology Co., Ltd.
We are one of the most professional thermal spray manufacturers and suppliers in China, also support customized service. Please feel free to wholesale high quality thermal spray in stock here from our factory. Welcome to view our website for more information.
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