The Complete Starter’s Guide to Spray Metal Finishing

Before considering metal finishing for spray processes, it’s important to consider one thing: this is a “starter’s” guide. This doesn’t offer detailed engineering information, this doesn’t offer safety or compliance standards, this doesn’t offer a means to avoid health and safety risks or to improve an already existing complex process. There are an indefinite number of resources that are much better suited to that – we love the ones provided by PCI (the Powder Coating Institute). 

All that being said, if you’re producing any kind of metal product and looking to evaluate any kind of spray finishing process for metal – whether it’s liquid painting, powder coating or sandblasting – this article is a great place to start because we’re revolutionizing how manufacturers can approach these processes through robotics.

There are three primary spray processes applied in metal finishing: liquid paint, powder coating and sandblasting. Each has its own merit and goals – paint may be easier to repair or more forgiving where baking is not required, powder may function for higher volume and preferred materials, sandblasting can provide the final finish that customers are looking for. Understanding how to maximize each process is critical to improving overall productivity. 

Liquid Paint Spray Metal Finishing

The primary goal of industrial paint is to provide both an aesthetic and materials-compliant finish that can be touched up or restored without significant challenge while also providing basic protection against surface damage and corrosion.

Paint is typically preferable for light-duty equipment or applications with defined maximum weights (often found in the aerospace industry). Generally powder coating or other media (ecoat, thermal spray and more) are considered as more useful, durable protective coatings for heavy duty applications and equipment. However, these are also costly and difficult to touch up. 

For instance, why aren’t entire cars powder coated? Well, if a car gets into an accident and does have inevitable damage, repair would entire re-coating the entire car and baking it to a finish. This may not be feasible or desirable given all the components that go into a finished car, where heavy equipment (like that for construction or snow removal) is usually practically designed and have many replaceable parts, which means damage can justify rework, recoat or an entirely new part (not to mention that these types of goods don’t generally receive as much as “give” damage in a crash).

So, how do you know if liquid paint is your best spray metal finishing process? Here are a few tips:

  • The primary goal of your finish is aesthetic and you have multiple options
  • The material being coated is not resistant to high temperatures (e.g. 350 degrees fahrenheit and up, as would apply to aluminium) that are required by alternatives like powder coating
  • High-gloss finish or easier touch-ups are more desires and preferred for the particular product being finished
  • You can’t afford the equipment that comes with powder recovery systems or you would prefer lower consumables costs overall

Powder Coat Spray Metal Finishing

Powder Coating is an electrostatic coating that is applied in a free-floating (but safely contained) environment to materials that can conduct electricity. This electromagnetic attraction allows the powder to “stick” to the surface of your metal products and then transit into a bake oven where the powder is essentially melted/”baked” on to produce a polymer-like finish after final cooling. 

Because of the nature of the coating, excess powder remains in the booth and as long as there is no cross-color contamination, it can be easily recovered and reused (with specialized equipment) to eliminate waste and reduce cleaning required in a booth.

Powder can also prove more durable in the long term, which is why it’s preferred for many applications from heavy equipment to fitness equipment to a variety of small tools and appliances that are deployed in rough circumstances. The total cost of powder can be much lower than paint in the long run, but equipment required may make start-up costs more expensive. 

At the same time, because powder sometimes requires a “spray and pray” approach, it can lead to excess coating beyond your actual thickness requirements. This is effectively the source of most “waste” in powder coating and even for small shops or lines can add up to hundreds of thousands in additional costs per year.

Overall, you should prefer powder for spray metal finishing if you need one of the following:

  • A strong, durable coating in a single color at a high volume
  • A matte-type finish with a fast, easy, forgiving and low-skilled application process
  • Highly automated coating with simple part shapes
  • Highly automated coating with complex part shapes (note: this is addressed through robotics rather than a fixed automated system, but the total price of each can actually be comparable)

Sandblasting Spray for Metal Finishing

Sandblasting or abrasive blasting is an important and sometimes the final step to spray metal finishing processes.

This can use a variety of different media to wear down, clean, smooth or flatten out a variety of surfaces in order to ensure that the final top-level coating applied can be sufficiently even to maximize results. 

As it happens, the way in which you want to achieve that best possible finish can vary depending on what media is best suited for the look. Everything from steel shot and grit to glass beads, different naturally occurring sands, walnut shells, corn cobs – all of these media and more enable you to achieve a refined look no matter what final finish you want to produce. 

Now, the challenge in sandblasting is more often how you want to apply this. A manual worker or generally automated systems can be helpful, but in situations where processes are predictable, robotics are generally preferred.

Processes must be very predictable for most robots, however. So, autonomous robots may actually be the best choice for highly varied sandblasting processes where parts or the shape of parts change frequently, but automation is still required. 

Taking Steps Towards a Robotic Process

While spray metal finishing requirements can vary both across and within industries, all industries are facing challenges in terms of both labor and skills shortages, as well as quality of output.

For both of these challenges, robotics is usually a compelling problem solver given its ability to predictably and reliably follow the same instructions over and over again.

Autonomous robots are able to provide this reliability and automation, but actually adapt to different parts and circumstances without the need for manual programming or jigging – an opportunity to improve spray metal finishing processes far into the long term. 

Omnirobotic provides autonomous robotics technology for spray and finishing processes. It’s revolutionary Shape-to-Motion™ approach can SEE parts, PLAN a unique program and EXECUTE it in real-time with existing industrial robot brands. Check out our payback calculator to find out if an autonomous robotic cell could be right for you.

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