The Stages of Preparing Sheet Metal for Finishing

You’ve found yourself working on a project that requires finished sheet metal to complete, and you're not sure where to begin. If you're used to working with pre-finished sheet metal or previously outsourced this step of the process, you might be wondering how much time it will take. How is applying finish going to alter your projected schedule?

You can't just apply the finish and call it good. The steps you must take beforehand are labor-intensive and require specialized chemicals to do correctly. But the good news is, it doesn't take much time at all. 

We wanted to break down the metal finishing process for people like you with this blog post. Once you know how to prepare sheet metal for finishing, you'll work more efficiently and be able to tackle a broader range of projects. So keep reading to add this valuable skill to your toolbelt. 

Step 1

Prepare Areas to Be Finished 

Depending on your project, not finishing your sheet metal may have an uneven appearance. For example, paint won't properly adhere to some aluminum. You can save yourself some time (and finish!) by covering any sections you can't apply it to with tape.

What tape you use mostly comes down to personal preference. However, for the sake of comparison, here's a comparison of the types most commonly used in construction projects:

Masking Tape: This tape is suitable for masking smaller surfaces because it leaves less sticky residue behind than other types of masking tapes. The only downside is that it can leave a small amount of residue depending on what type of sandpaper or steel wool you're using for sanding.

Duct Tape: Though generally used for home repairs and such, it's another excellent choice for protecting metal. However, the adhesive will leave some residue that you could either sand off or use chemicals to remove.

Painters Tape: Painters tape is great because it shouldn't leave any residue behind, and it sticks well to multiple surfaces. The only downside is that it can start to peel off if left for too long, so you should apply it at least twenty-four hours before you intend to begin the preparation process.

Step 2

Cleaning the Metal 

Once you've protected any parts that don't require a finish, it's time to start cleaning. When it comes to finishing sheet metal, cleaning is a vital step that you cannot afford to do by half-measures. If you don't clean the surface appropriately, your finish won't adhere, and you'll have to repeat the process.

You cannot simply eyeball the metal to confirm that it's clean. Even small debris, like sand and dust, will result in noticeable spots later on. What's more, grease can remain on sheet metal from its manufacturing process.

A good deep clean starts with degreasing agents, which come in wet and dry forms. Both are effective, varying only in how you use them, so be sure to follow their instructions carefully. And don't forget to wear appropriate safety equipment when handling these chemicals! 

Next, completely remove the degreaser from the metal. Any that remains will prevent the finish from fully adhering to the metal. Wash with a mild detergent and thoroughly dry.

Step 3

Remove Impurities

Your sheet metal likely contains impurities from the manufacturing process. Shortly after pressing, each sheet is dipped in a metal pickling solution to remove them. However, pickling often creates new impurities, albeit in a lesser amount.

It's best to play it safe and sand down the exposed sheet metal, just to be sure. Start by scrubbing all sides with 150 grit sandpaper and smoothing out all rough edges. When finished with this step, wipe down your sheet metal one more time before applying any finish.

Optional Step: Start Again 

It can be difficult to detect every impurity still on your metal. So rather than fretting over each step until you're absolutely certain, another approach is to simply run through steps two and three again before moving on. This method removes doubt by giving you visual evidence of debris reduction.

Every time you clean and remove impurities from your metal, you'll notice less dirt and debris gets removed each time. Using this as a guide, you can repeat the process until you're satisfied. However, keep in mind that sanding too much will wear down the metal, so work towards satisfaction rather than perfection.

Step 4

Apply Your Finish 

At long last, it's time for the finish. But, don't skip out on the safety equipment! These chemicals are safe for metal but are harmful if they contact exposed skin.

Apply a small amount of your finish over the sheet metal until it is fully saturated. Let it rest for at least twenty-four hours or until it has completely dried. Afterward, grab some steel wool and start scrubbing until your metal has a shiny appearance.

All you have to do is remove the tape from the first step, and that's it: you're ready to apply paint over the finish and use the metal as needed. All told, it shouldn't take longer than two days to successfully prep your sheet metal for finishing.

Learn More About Metal Prep With Engineered Mechanical Solutions

Learning to prep sheet metal will help make you and your team more self-sufficient, saving time and money. But some procedures are too specialized to tackle on your own. When it comes to manufacturing services, you need a partner with experience. 

That's why we're here.

Since 1990 our team at Engineered Mechanical Systems has provided project managers with custom fabrication and machining solutions. We've equipped our facility with the latest industry-standard machinery, but more importantly, our staff of passionate and experienced professionals. We're here to help you to get the right solutions every time.

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