Industrial Coatings: The Pros & Cons of Overcoating

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Many of the challenges that are faced within the industrial coatings industry are a result of ever-evolving environmental conditions. Every field environment is unique to its specific industry and location. For example, a water tower with a lead-containing coating that is located in a suburban neighborhood would have very different requirements compared to process piping in a refinery.

Yet, asset owners and contractors face similar challenges and cost considerations in both environments. Blasting and painting assets within city limits require containment, cleanup and possibly lead abatement procedures to ensure the safety of the surrounding population. The same is true in a refinery, where protection is necessary for rotating equipment and drains. You may even need to obtain special permits, such as hot work permits.

Fortunately, there is a solution that can help mitigate the asset owner's overall investment for these project types, while still ensuring safety for the contractor: overcoating. The process of applying an additional protective coating over an existing coating, overcoating can offer significant time and cost savings—but it cannot be used in every situation.

In this article, we will discuss some of the main advantages and disadvantages of overcoating, and whether it makes sense to use it as a solution for your next coatings project.

The Advantages of Overcoating

1. Overcoating Requires Minimal Surface Preparation & Cleanup

Have you ever worked in a facility that needed a facelift due to a coating that was weathering away? Was there anything wrong with the coating other than its aging? For example, maybe this facility was recently bought out, and the new owners wanted to change the color to match the company's other facilities.

Regardless of the reason at play, completely removing an existing coating and recoating an entire facility is often not a practical option due to the significant time and costs involved. In a case like this, overcoating is often the perfect solution to this problem.

Many high-performance coatings require minimal surface preparation before overcoating, which in turn saves considerable time. This is especially true for coatings with excellent wetting abilities, such as Rustbond. These cross-linked, penetrating coatings wet-out and bond to the weathered, pre-existing coating and prepared corroded areas—ultimately creating a barrier that acts as a tie-coat over which you can apply a topcoat.

Surface preparation can also cause downtime for hot work permits if extensive surface preparation by power tools or abrasive blasting is required. Since overcoating only requires a clean, dry substrate, there is typically less downtime, allowing for more application time throughout the day.

2. Overcoating Generates Cost Savings for Application

Remember our above example of the elevated water tower with a pre-existing, lead-based coating? Rather than removing that existing coating, it could instead be pressure washed and overcoated. This method would save significant costs related to lead abatement, such as mobile shower units, containment, cleanup and disposal.

Since overcoating reduces the time needed for surface preparation and cleanup, it ultimately decreases the overall cost for the application. This allows for the completion of more maintenance work, given that the price per square foot is lower. Additionally, since many of the high-performance coatings on the market are high in solids by volume, they can cover more square footage due to a lower VOC.

The Disadvantages of Overcoating

1. Overcoating Increases Surface Tension

As you apply more coats to a pre-existing coating, you in turn increase the overall surface tension. If the pre-existing coating is over 15 mils, overcoating may not be an option considering that the system is only as good as the initial surface preparation.

2. Overcoating Can Have Adhesion Issues

An overcoat may not adhere properly to a pre-existing coating. Before giving overcoating the green light, you should first apply a test patch of the overcoating system, then perform adhesion testing by following standards such as ASTM D3359 – Rating Adhesion by Tape Test or ASTM D4541 – Pull-Off Strength of Coatings Using Portable Adhesion Testers. This will serve as a baseline to determine whether the asset can be overcoated.

3. Overcoating May Cause Premature Failures

In the field, assets have often been overcoated multiple times—with the coating now showing signs of stress, such as brittleness, cracking and checking. It’s important to know that these assets are not good candidates for further overcoating. Overcoating under the wrong conditions can cause premature failures, such as delamination.

4. Overcoating Results in a Longer Drying Time

Another disadvantage is the drying time of a penetrating sealer that is overcoated. When using a penetrating sealer, the dry time is usually much longer because the sealer needs to stay in a wet stage for more time to properly wet-out the surface of the existing coating. As a result, this can cause unwanted downtime in certain phases of a project.

As you can see, there are a wide variety of factors at play that can determine whether an asset is a good candidate for overcoating. Although overcoating can provide faster results at a lower investment than more traditional methods, it’s important to first weigh the advantages and disadvantages of overcoating as a potential solution for your particular project.

Need Help Determining if Overcoating is Right for Your Project?

Contact Carboline’s team of technical service engineers to determine if overcoating is a viable option for your next project.

Powder coating is an advanced method of applying finishes to metal for either protective or decorative reasons. It provides durable finishes in a wide range of color options and is considered to be a better alternative than traditional liquid paint coats.

Here are ten advantages and disadvantages of using powder coating:

Pros

1. Strong coating

Powder coating provides a durable finish that’s far stronger than what liquid paints offer. These coats are known to protect equipment in the harshest environments without compromising on the aesthetics of the finish. As a result, it’s common to find such coating used on large industrial equipment, structures, and oil field supplies. View our gallery to view our powerful coating work for a diverse range of customers.

2. Affordable

Powder coating is also affordable with the application process eliminating many extra steps and drying time that comes with liquid paint. The raw material powder is less expensive than wet paint and can be stored away in far less space than what traditional paint cans would need.

3. Various colors and finishes

Powder coating offers many colors and finishes. One can also easily have custom colors made by the manufacturer quickly, and there is a broad range of finishes from high gloss to matte. It’s even possible to customize the texture of the coat (e.g., texture or metallic).

4. Low maintenance

Powder coatings require little maintenance after application. Since the coating his highly durable and resistant to corrosion or scratches – there’s never a pressing need to use cleaning solutions or solvents to keep the surface in tip-top shape. Generally, you can expect to clean the applied coating only a few times a year.

5. Quick application

Powder coating is applied using an electromagnetic charge. This means there’s no need to wait for the coat to dry before applying another layer while applying the coating. It can all be done in one go with very little waste creation.

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6. Even application

The application of powder coating also results in an even finished horizontal and vertical surface. This is due to the process of spraying and rapid heating to apply the powder coating. With liquid paint, you would run the risk of drips forming.

7. No toxic fumes

Liquid paints are known to release toxic fumes from volatile organic compounds into the air. With powder coatings, this risk is non-existent or very little, making it a far safer option to use.

8. Low carbon footprint

Powder coatings are also known to have a low carbon footprint throughout their value chain. This is great for businesses aiming to switch to more environmentally sustainable materials in their manufacturing process.

9. Recycle friendly

Liquid paints commonly create unwanted waste that needs to be disposed of properly. Powder coatings, however, can be recycled and reused. This makes them a more environmentally friendly, cost-effective, and efficient coating to use.

10. Greater transfer efficiency

While liquid paint coats have a transfer efficiency of 30% and nearly half of the product evaporates away. With powder coating, you get a 65% transfer efficiency on average, with any overspray recovered to be used again in the future as needed.

Cons

1. Can deteriorate from UV light – Depending on the powder chosen

As with any coating, over time, there will be gradual fading. Powder coatings are known to react strongest to UV light and contribute most to its fading. However, there are additional UV protective coats that can be applied to mitigate this.

Related: Find the Right Powder for You

2. Huge start-up cost

The application of powder coating can have high start-up costs. An electrostatic booth and oven are required to apply powder coating. Both of these are expensive to acquire and the cost to keep an oven running can be high. This makes it a less common coating option for low volume or small projects, not to mention for getting ISO certified and PCI certified.

3. Difficult to do thin coats

When looking to apply extremely thin coatings, powder coating may not be the best choice. The thinnest coating that can be applied without seeing a drop-in quality is 40 to 60 microns. For anything thinner than this, it’s advisable to use liquid paint instead for a better finish.

With ABITL’s new “MIL GAUGE GUN” we can take real-time measurement to apply the perfect amount of powder every time.

4. Slow color change vs Competitors

During the application process, color changes are common where machinery is cleaned of the previous coating color to be ready for a different one to applied. With powder coating, this can be a long process due to the greater risk of cross-contamination occurring if the machinery isn’t cleaned properly.

However, ABITL’s process is a state-of-the-art system that allows the cleaning process to be as fast as 5 to 7 minutes.

5. Powders can’t be mixed to make different colors

With liquid paint, it’s common practice to mix various paint colors to form new ones. With powder coating, this isn’t possible as the different polyester powders when mixed and applied won’t result in a new color forming. However, to combat this, there is a much wider range of powdered coating colors that one can buy. ABITL offers coating in a wide range of colors. Check out our powder suppliers to figure out which has the right one for you.

6. Specialized equipment needed to apply powder coating

Another disadvantage to powder coating is the need for specialized equipment such as electrostatic sprays. Moreover, the surface on which powder coating needs to be applied must be conductive. This creates limitations and can hinder how well the powdered coating reaches into deep recesses.

Since ABITL is a multi-million dollar facility with back up parts, the specialization of powder coating equipment does not pose a problem.

7. All coating needs to be baked in an oven

With powdered coating, there is no option but to use an oven for baking the powdered coating during the application process. It’s not possible to carry out an ambient cure. One minor problem is that the application process can be more expensive and longer.

8. Difficult touch-ups to execute

With liquid paints, it’s easy and convenient to perform minor touch-ups to any applied coating as needed. However, this powdered coating isn’t as easy and requires the entire process to be carried out.

Since ABITL has worked with many suppliers, diverse experience means an ability to touch up just about any coat.

9. Doesn’t work on a wide range of materials

As mentioned earlier, for the powdered coating to work, you need a conductive surface for the charged paint particles to attach to. As a result, the powdered coating is limited in the materials it can be applied to. Due to the use of an oven, one can’t apply powdered coating on materials that may melt such as rubber.

10. Less control over the process

The last disadvantage to powder coating is the lack of control over the application process. Compared to liquid paint coats, there’s less control over the smoothness of the coat and the amount of coating that can be applied.

With more than a dozen powder suppliers and their technicians we have control and can deliver a perfect coating every time.

ABITL are leaders in the powder coating process. With our own high-volume automated powder coating line, you can have high-quality coats applied in on-time and on-budget. With over 50 years of experience in powder coating, our Eighty-foot powder coating capacity can handle any volume of work sent our way.

Get in touch with us for your metal finishing needs today.

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