If you are looking to sand aluminum for your next home improvement project and do not know what grit of sandpaper to use for it, you have come to the right place. We researched this topic to give you the answer and more.
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For general aluminum polishing, you can start with 320-grit sandpaper and steadily work your way up to finer grits until you reach the desired sheen. If it is heavily tarnished or needs a lot of sanding, start at 180-grit. Never use anything coarser than 180-grit, as it can damage aluminum.
Before you buy sandpaper sheets for your next project, read on to discover the best practices and pitfalls to ensure a top-notch job at sanding your aluminum materials.
What Grit Sandpaper For Aluminum?
In simple terms, grit is the rating that describes the texture of sandpaper. A lower number means coarse sandpaper; a higher one means fine sandpaper. Meanwhile, sanding means stripping off the outermost layer using an abrasive (i.e., sandpaper). The coarser sandpaper is, the faster it will eat away at the target material.
You might be inclined to opt for the lowest grit available at your local hardware to finish the task faster. However, low-grit sandpapers tend to introduce new, visible scratches—especially to softer materials. And among the common metals, aluminum is notable for being on the soft side of the spectrum.
Aluminum naturally reacts with water or air, forming a thin layer of aluminum oxide (a.k.a. alumina) on the surface. The layer of alumina is what makes it appear dull or faded. Removing the alumina through sanding will expose the fresh aluminum with an inherently fresh sheen.
The typical reasons for sanding aluminum include polishing, edge deburring, and removing scratches. Going overboard by using the coarsest grit you can get your hands on will produce damage that wasn't even there to begin with. That means double the work.
For General Polishing
For general polishing (or to smooth out minor scratches), you can start with 320-grit sandpaper for the first pass. Go up to 400-grit for the second pass, then finish with 600-grit for the third pass.
Do not be too surprised to watch your aluminum workpiece transform right before your eyes as you switch to finer grits with each pass. After the third and final pass, it will shine like it's brand new.
If you want to bump the luster up, you can go up to 800- to a 1,500-grit for the final pass. Nonetheless, ending with 600-grit is perfectly fine for most applications.
For Heavy Sanding
You'll need to remove more material when dealing with sharp edges or deep scratches. Using a coarser grit when sanding will make the job faster. For this, you can use 180-grit sandpaper.
You may encounter sharp edges, especially if your project involves cutting aluminum. It is a good idea to deburr the edges to avoid cutting your hands accidentally.
Deep scratches can be very visible on aluminum. To remove those eyesores from your project, sand away using 180-grit. Don't go coarser than 180-grit even if you are tempted to rush the job. You could end up making it harder than it should have been.
What's The Best Way To Sand Aluminum?
Now that you know the basics of sanding and which grits to use for each pass, there are a few best practices and tips that you can take into consideration for your next project that involves aluminum.
Sanding aluminum—or any material for that matter—is not just about scrubbing the workpiece. You could be wasting money (and precious time) by sanding aluminum the wrong way.
The good news is that there is a straightforward way to achieve the best results when sanding aluminum. Here is a 3-step process that can help ensure a top-notch outcome.
You must remove any dirt from the aluminum surface. If you need to scrape off some stuck-on debris, you can use a stainless steel wire brush to chip away any dirt your aluminum workpiece might be housing.
Just make sure that it's the stainless steel kind and not carbon-based to avoid introducing the possibility of rust. While aluminum itself doesn't rust, scouring it with an abrasive material that does rust such as carbon-based wire brush can leave behind microscopic remnants of the bristles in the workpiece.
After removing what you can with the brush, scrub the aluminum workpiece with regular dish soap or a mixture of vinegar and water to loosen up dirt, oil, or grease.
Paint thinner or degreaser can also help, especially when you are up against exceptionally stubborn gunk. Rinse well with water and let it dry completely.
Allot the majority of your time and effort into diligently sanding the aluminum. As described earlier, you need to start at 180-320 grit, depending on the severity of the case. Then, constantly move up to finer grits with each pass.
You can sand smaller pieces of aluminum by hand. All it takes is a bit of patience and some elbow grease. However, when renovating something larger like a table, power tools like orbital sanders or angle grinders can benefit you greatly.
After sanding, all you need to do is to buff the aluminum. Aside from maximizing luster, buffing the surface protects the natural sheen of bare aluminum. The polishing wax covers the aluminum, acting as a barrier against dust and debris.
For hand-buffing small items, you will need a few sheets of clean cloth and aluminum polish. Take note though that aluminum polish is dangerous when ingested. For a food-grade alternative, you can make a homemade paste by combining cream of tartar (potassium bitartrate) with water.
Start by applying a bit of aluminum polish (or your food-grade paste) on the workpiece using a clean cloth. Use small, circular motions to spread it evenly. Finish it off by removing the excess polish using a fresh cloth, mindfully maintaining the circular wiping pattern.
Similar to sanding larger projects, buffing can be made easier with the help of trusty power tools. You can use an angle grinder equipped with an airway buffing wheel to bring out the real shine.
What Abrasive Is Best For Aluminum?
Aside from considering sandpaper grit, you must choose between different abrasive grains. These refer to the type of material embedded in the paper or cloth backing.
Experts recommend combining the two most common grains: aluminum oxide and silicon carbide.
Aluminum oxide sandpaper is the cheapest and most common grain in most hardware stores. It is very durable, so you can use it for your first pass to bump off the initial roughness or corrosion.
Whereas aluminum oxide works best as a starting point, silicon carbide sandpaper will allow you to smoothen your workpiece further because it is the sharpest abrasive grain. Use it for the succeeding passes to achieve the desired level of sheen.
Start with 180-320 grit sandpaper for your first pass depending on the severity of the case. Work your way up to finer grits until you're happy with the shine it casts. Don't go coarser than 180-grit to avoid unintended damage to your aluminum workpiece. Now that you know what grit of sandpaper to use, you'll be better prepared for your next project.
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