Pretreatment Prior to Coating

Pretreatment Prior to Coating

A perfect coating is dependent on a metal surface that has been well prepared. Various metal surfaces are often pre-coated with dirt or oil from other processes that prevents perfect coating of the surfaces. Some are hard to see, but they are lurking there. No matter what type of coating you are using, a non-clean surface will prevent proper adhesion and reduce overall quality and appearance of the finish. Avoid FAILED parts. Who needs pretreatment prior to coating = everyone!

Not all Pretreatments are created equal, but typical stages you need to consider depending on your material sub straight, what you are cleaning off and overall required specifications for finish, you could be dealing with a simple single stage or up to 9 stages including a mix of the following: This can be done in a dip or spray.

Cleaning with Detergent / Heat = Cleaner solution concentration and temperature are regulated at this stage to get desirable results. Proper draining is also important to prevent cross contamination from a wash to rinse. Don’t let parts sit around after cleaning, move straight into the next step.

Rinsing for the Detergent = the removable of alkaline from the detergent and getting to a clean surface. When performing rinses, dry the surface as quickly as possible to avoid flash rust on the newly prepped surface, if the process stops here.

Conditioning Stage = sets the surface to a certain pH level, and then locks that pH level in.

Phosphate = laying down a protective barrier that will prevent corrosion and oxidization of the metal, giving it a longer life. Could be zinc, iron or zirconium.

Rinsing for Phosphate = Once the conversion coating has been applied, another rinse stage is required, performed just like the previous rinse stage

Passivation Rinse or Sealing Stage = The chromic rinses serve the following purposes: (1) dissolution of any water-soluble salts in the pores of the phosphate coating or their conversion into insoluble water salts; (2) improvement of salt spray resistance by coating the surface with soluble chromate and; (3) formation of a thin oxide film in all pores of the phosphate coating. Thus, there is an excellent need for pH control at this stage. Proper water treatment for dumping needs to be considered at this stage.

Final Rinse = RO or DI rinse – meaning no chlorides or fluorides in the water.

Dry Off Stage = A perfect dry-off process exhibits parts with an ideal uniform surface appearance. The presence of any streaks or splotches leads to the low durability. Proper temperature is important at this stage.

With pretreatment being such an important step in the finish process, automation can play a large role in meeting your production needs. Labor is becoming increasing harder to find and maintain in the dirtier jobs. The process is hard on the body and often unsafe when trying to clean in a manual process. Grueling work. You can’t walk away mid-process, leave it, and then come back to it. It simply won’t work.

When looking to automation you can take the process to a self-contained system managed by the push of a button. Reducing handling and even automate the load and unloading process, so many options in today’s world of manufacturing. Don’t get stuck in yesterday’s limitations.

Don’t miss an important step, reach out to the professionals. LS Industries has been designing systems for 46 years. Made in America for ease of maintenance.

Other considerations: space, product mix, proper grounding, production rates needed, room to grow, electrical requirements, heating, wastewater treatment, paint equipment required, storage, ovens – VOC generation, humidity control, keeping a clean environment, handling. WE DO IT ALL.

Need to remove rust from your stored materials prior to washing? We can help with that too. An alternative, pretreatment to plain shot blasting is to combine a shot blast with a zinc rich or epoxy primer. Using this method, you clean the substrate with the shot blast and lay down a corrosion resistant layer through the primer that the coating can adhere to. Your one stop shop for accountability in surface prep and finish. From batch to full inline….let’s talk about your dirty parts!

Melissa Gibson (Palmer)

East Coast Sales

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