Metal Polishing: How To Polish Stainless Steel & Aluminium

Humans like shiny things. It’s in our DNA. An evolutionary artefact from a time when the glimmer of water was a beacon of survival. Nowadays, with water literally on tap, our deeply-rooted reflection-obsession manifests itself in our love of glossed up metal.

Whether you’re restoring a beautiful vintage car, doing home renovations or shining up an antique, there are some basic guidelines you need to follow in order to get the best results for your project.

The process for polishing stainless steel does vary from that of aluminium, so we’ve broken it down for you in this easy to follow guide.

Polishing stainless steel: basics

The tools and techniques you use are going to depend on the size of your project, the initial condition of the steel and the end result you’re looking for. If the steel is scratched or dented, you’ll need to prepare it before polishing so you don’t end up with a shiny surface beautifully highlighting all the imperfections.

First things first, make sure the surface has been thoroughly cleaned. A simple detergent may suffice. If you’re working on an automotive project and have bitumen spots on the steel, kerosene does a brilliant job of dissolving the tar with minimal effort required.

If there are scratches to remove, you can use sandpaper, gradually progressing from coarse to finer grit until you have a smooth, uniform surface.

To get a professional finish on your stainless steel, it’s important to use equipment that maintains constant speed and abrasives that can maintain their grit for an extended period. The machinery you choose will depend on the nature of your project. For smaller jobs, you can use a drill or dremel with polishing attachments. Larger projects may require a grinder with polishing wheel. There’s also a range of machines that can completely automate the process.

A quick note on safety: make sure you wear goggles when working with metal, particularly while operating machinery. Getting a fine bit of metal stuck in your eye is not fun, especially since your salty tears create the perfect conditions for rust to form around the metal (not kidding, you can get rust in your eyeball).

Mill finish

Otherwise known as a matte finish, the milled look is pretty bare-bones. It’s inexpensive, less time-consuming and great for surfaces that don’t need to be overly attractive (think kitchen sinks and metal work benches).

This is the pre-polished look that you’ll get after using the finest grain abrasive. It gives you a smooth, less pitted surface and is great for practical applications. From here, you can continue the polishing process to create more visually appealing looks.

Brushed finish

Brushing the stainless steel produces a pattern of light, parallel lines. It creates decorative appeal without reflectiveness, making it great for surfaces that will be exposed to a lot of sunlight or bright indoor lights. It’s often used for kitchen appliances because no-one likes being blinded when they’re just trying to make their morning cup of coffee.

Keep in mind, this finish does reduce the corrosion resistance of the stainless steel. If you live close to the beach, it may be worth investing in a rust-proofing option suited to your project.

You’ll want to work with a high quality abrasive and set your machinery up so you can create uniformity with the lines.

Mirror finish

Mirror finishes are highly reflective and created by continuing the progression of finer abrasives and adding in a polishing compound. This creates that shiny look we humans are so drawn to while, as a bonus, making cleaning easier. It’s also great for masking the after-effects of welding.

Unlike the brushed finish, a gloss finish actually improves the corrosion resistance of the stainless steel. The polishing smooths out crevices where rust particles collect and take hold. With patience and attention to detail, you can create a chrome-like shine, making this process perfect for automotive work.

For this finish, it is even more essential to ensure you’ve gotten rid of all scratches and defects as they will stand out even more on the finished product. Once your surface is adequately prepared, you can set yourself up for polishing. A grinder with polishing wheel can be used, along with a high quality polishing compound, to create an even shine. To get it to a brilliant mirror-like gleam, you’ll need to then buff the surface, for around 5-10 minutes, with a clean cloth and polishing compound.

Polishing aluminium: basics

Aluminium can be difficult to work with, especially if you’re looking for a brushed or polished finish. Once again, you want to ensure your surface is clean and well prepared. A non-woven, coarse, surface conditioning disc will help grind down welds. You can get these in belt or disc form, depending on the machinery you’re using.

Mill finish

An aggressive abrasive, like a 36 grit sanding disc, will help you achieve the basic Mill finish. These abrasives are available in diameters of 50mm right up to 180mm.

Brushed finish

Depending on the depth you’re looking for, you can use coarse, medium or fine abrasive discs or belts. A finer abrasive will create a lighter brushed finish.

Mirror finish

As with the stainless steel, you can achieve a chrome-like mirror finish on an aluminium surface. The glossy look does take time, patience and methodical work. The smoother you get the aluminium, the more mirror-like it will be when you are finished. Using stitched cotton mops and grain pastes, you simply work your way through finer grains until you reach a gleam you’re happy with.