Different Types of Pretreatments for Powder Coatings
Different Types of Pretreatments for Powder Coatings
We always strive to be the best with our coatings and we know how important it is to apply these coatings to prepared substrates, so let's take a look at some of the many ways we do this. A good preprocessing process can be as simple as 1-2-3.
But what is a preprocessing system? Simply put, they are the process of cleaning surfaces and preparing them for coating. Anyone working with paint should be familiar with this process, and it benefits both the customer and the paint dealer. Pretreatment produces a surface to which the coating can adhere, whether the coating is liquid or powder. Additionally, pretreatment increases the performance value of the coating, extending its life and helping to prevent corrosion. That's the how and why of preprocessing, but who and when? We'll start with the first one. So, who should use preprocessing? The answer is everyone. Anyone who wants to clean their hands at the end of the day knows that they've sent out a quality product that should pretreat the substrate. Cleanly, the substrate must be prepared before any type of coating is applied to the surface. The point of pretreatment is to prepare the surface for any type of coating and prevent it from degrading on the production line. There are many different pretreatment methods and various types of pretreatments available, and often depend on the substrate you are coating, the end use of the part you are coating, or the size of your coating line. Pretreatment processes are automatic and manual, multi-stage and single-stage, and some are better for steel than aluminum. The good news is that there is a wealth of information available and some excellent pretreatment suppliers with the knowledge to help you make the right decision for your line. So let's look at the different stages of a good preprocessing system, and then look at the various possible combinations of these stages. We'll go into more detail on these below - but, when should re-treatment be done?
pretreatment process
All good pretreatment processes start with a basic cleaning process. If nothing else, this is the phase that every job shop should go through.
cleaning phase
Whether you are new to surface preparation or a veteran, you know that the cleaning phase is the most important and essential phase in preparing any substrate. Oil, dirt and grime can damage even the most carefully applied coatings, affecting the finish and the long- and short-term performance of the products you apply. You don't want to waste your time and money, and you don't want dissatisfied clients choking your neck. Cleaning is relied upon at every stage thereafter, including successful powder application. The following preprocessing stages will not work properly if not done correctly. There are many different types of cleaners, the most commonly used are acids and solvents. These cleaning solutions are usually sprayed onto the part or the substrate is dipped into a bath of solution. Heating the cleaning fluid usually makes the cleaning agent work better. Using the parameters provided to you by the preprocessing vendor will be the key. Most importantly, it's important to make sure you run the process right away and don't let the freshly cleaned parts sit. You can't wash it, leave it for 10 minutes, then go back to it and spray some more, then let it sit before it dries. You have to build a continuous process based on the product you are using. Then let it sit before it dries. You have to build a continuous process based on the product you are using. Then let it sit before it dries. You have to build a continuous process based on the product you are using.
rinse phase
After cleaning, enter the rinse phase. It's important to remove all dirt, grime, and possibly the occasional dead bug, but it's also important to remove the residue of any chemicals used to clean the surface. This is the key to keeping the coating free of contamination. While these flushes can be performed with regular city tap water, reverse osmosis (RO) or deionized (DI) flushes are preferred. This simply means that water is treated to remove fluoride, chloride and all other substances that are added to the water, which are chemicals in nature and we don't need to be involved in the coating process. When rinsing, dry the surface as soon as possible to avoid flash rust on freshly prepared surfaces. Remember that any runoff needs to be handled with care.
Conditioning stage
Preparing the surface to receive the product for best results requires some kind of conditioner. Essentially, with a conditioner, you set the surface to a specific pH, then lock in that pH. Doing this creates a surface that is ready to receive the next layer of preparation.
zinc phosphate stage
We call this the zinc phosphate stage because zinc phosphate is highly regarded as an excellent chemical conversion coating, but it can also be iron phosphate or zirconium, which can also be very protective. Not surprisingly, what this stage does is form a layer of zinc phosphate on the substrate. It's a bit like laying down a protective barrier to keep the metal from corroding and oxidizing, making it last longer. Once the conversion coating has been applied, another rinse phase is required, just like the previous rinse phase. Adding any type of phosphate stage to your pretreatment process means improving the performance attributes and quality of your work for your customers. Doing the job well is doing the job well.
seal stage
Sealing helps paint adhere to the surface, which means a higher quality finish to the final product, both initially and on the production line. There are several sealants, including chrome sealants, non-chrome sealants, and dry-in-place sealants. These allow for greater corrosion resistance - an essential quality for any substrate that will be exposed to the elements. It should be noted here that the use of chromium is extremely dangerous and dangerous. Using it requires specialized equipment and training. Chromium has been banned in some states in the United States. At the end of this phase, you will need to do another rinse, but it will have to be an RO or DI rinse - which means there is no chloride or fluoride in the water.
drying oven
The final stage is just drying the parts. It sounds obvious, but it's very important. The freshly prepared substrate must be dry, otherwise the powder will not apply correctly. A dry oven basically quickly removes any moisture left on the part after the last rinse. The longer moisture stays on the part, the more likely it is to form a layer of "flash rust". Allowing the part to dry quickly reduces the chance and also heats the part slightly in preparation for powder application. Obviously, the 8-stage process we just went through is a major undertaking, an automated production line process with all the cost, space, water treatment and maintenance requirements. This multi-stage pretreatment process will provide excellent results for pretreatment consistency, high corrosion performance and guaranteed high volume production lines. However, not every coater needs or wants to delve into pretreatment. Fortunately, pretreatment suppliers have created a range of smaller spray systems that also provide great results.
