Getting everything right is essential when it comes to metal spraying. To achieve metal spraying expert results, there are a few things you must focus on such as surface prep, equipment settings, and process control.
How to Achieve Optimal Results in Metal Spraying
Metal spraying is a process in which a coating material is heated until it becomes molten. It’s then sprayed onto a substrate where it solidifies and bonds on contact, forming a durable and wear-resistant coating. If you’re looking to find out how to get the best results, here are 6 steps to follow!
1. Surface Preparation
Surface preparation is arguably the most important step in the metal spraying process. It is thought that around 60-80% of coating failures are due to poor preparation. To ensure you nail this step, it’s important to clean your metal thoroughly. This means that all oil, rust, old paints, and contaminants must be removed.
Grit blasting the surface of the metal also helps with the preparation. Using sharp and angular media such as aluminum oxide creates a rough profile. Ideally, the surface roughness should be around 3.5 – 6.5 microns. Finally, you should use a bond coat on your metal surface. For better adhesion, apply a thin layer of nickel-aluminum or similar bonding materials. This should especially be done on smooth or corrosion-prone metals.
2. Choose the Right Spray Method
It’s important to note that there are a range of different methods to suit different materials and applications.
- Flame Spraying is a cost-effective method which is best for large surfaces. Although it is important to note, this method tends to have lower adhesion than others.
- Arc Spraying is a good method to use for structural steel. It is best for zinc and aluminum coatings due to corrosion control.
- Plasma Spraying is fairly costly, but it has a high-quality finish. This method works best for ceramics and high temperature materials.
- Hight Velocity Oxy-Fuel or HVOF is a very dense and strong coating for metals.
- Cold spraying works best for heat sensitive materials. This method is effective as there is no oxidation involved. There’s also minimal substrate stress.
3. Set Proper Parameters
When looking to achieve optimal spraying results, consistency is key! It’s important you follow these steps:
- Spraying distance should be kept at around 4 – 8 inches (or 100 – 200 mm) depending on the process. This helps to gain an even finish on your metal.
- The angle of the gun is another important factor. The gun should be kept perpendicular to the surface at a 90° angle. This helps with the buildup of the paint.
- The travel speed of the spraying should be even and consistent passes. The sprayer should avoid overlapping too much or too little for the perfect finish. Staying consistent with the speed means that the finish will be even.
- The paint temperature should be substrate. Overheating should be avoided as this can cause oxidation or poor bonding and ultimately tamper with the finished results.
4. Control Environmental Conditions
To gauge the perfect metal spraying conditions, there are several factors that should be considered to achieve optimal results. Firstly, high humidity should be avoided. When moisture is present, it can cause poor adhesion. It could also lead to corrosion under the coating.
Another way to control your spraying environment is to use extraction systems. This means the chemicals from the coating can be extracted safely, especially in enclosed and indoor environments. The temperature of the environment is also a major factor. It is essential to keep the parts and materials for metal spraying within the recommended range.
5. Inspect and Test Coatings
Another key to achieving your desired spraying results is to test and inspect your coatings. This can be done in a number of ways. Visual inspections allow you to look for porosity, cracking, or even delamination within the coatings. Another test that can be carried out is adhesion testing. The thickness of the coating can also be measured using ultrasonic or magnetic gauges.
6. Post-treatment Care
Sealing with the coating is a way to help your results last longer. Porous coatings such as zinc or ceramics can benefit from applying a sealant to enhance corrosion resistance. To achieve tight tolerances and smooth finishes, machining or grinding the coatings can help with this.
Avoid These Common Mistakes for the Best Results
As mentioned throughout the blog, there are a number of things that can have a negative impact on your metal spraying results.
- You should never spray on an unprepared or oily surface as this can affect the adhesion of the coating.
- You should avoid using the incorrect angle of the gun. Keep a consistent spraying distance to achieve an even coat.
- Don’t be inconsistent with the travel speed of your spraying as this can cause an uneven buildup.
- Never skip bond coating on tacky materials. This could lead to adhesion issues with your coating.
Use Alphatek: Metal Spraying Experts
With over 20 years of industry knowledge, using our expert services here at Alphatek ensures that you get the best metal spraying results every time! Our spraying services are ISO approved, meaning you can be assured that your expectations are always met. Our work also has multiple industry approvals including Oil & Gas, Rail, Aerospace, Automotive and more!
Our Metal Spraying Experts use in-house R&D and Met Lab facilities to offer bespoke applications and solutions tailored to your needs. Our friendly, expert team is reliable and there to assist every step of the way. Get in touch with us today to see how we can help you!
