Many fabricated aluminum pieces have to be anodized before you can use them in various applications. The additional layer shields aluminum from corrosion, wear, and abrasion. Furthermore, anodizing increases aesthetic appeal as you can apply various colors and finishes. However, the result of aluminum anodizing depends on the state of the workpiece before the process.
Cleaning aluminum before anodizing is important because it helps remove contaminants and improve the adhesion of the anodic layer. If you are wondering about the best ways to clean aluminum parts before anodizing, you are not alone. This article will provide a step-wise guide on how to effectively clean aluminum, why cleaning aluminum before anodizing is essential, and tips to get the best results.
Contents
What is Anodizing Aluminum
Anodizing is an electrochemical process of converting the surface of the aluminum metal into anodic finish. This extra layer serves both aesthetic and functional purposes. It is durable, attractive and helps the final parts withstand corrosive attacks when used in demanding applications. You carry out the aluminum anodizing process by submerging the prepared workpiece into an electrolyte bath solution. You then connect to a power source.
The workpiece attracts the negative oxygen ions to form aluminum oxide. The oxide layer continues to grow to produce a porous and ordered structure. The final step of aluminum anodizing is sealing the pores using hot deionized water. Note that this extra layer originates from the aluminum metal itself rather than applied to the surface. Hence, the anodized aluminum does not peel or chip even after prolonged use.
Why Clean Aluminum Before Anodizing
Cleaning is an essential part of aluminum workpiece preparation before anodizing. Adequate cleaning helps to remove contaminants such as dirt or grease that can interfere with the anodizing process. They affect the quality of the anodic layer and can result in flakes, stains, spots, or shiny dots. These surface impurities and inconsistencies affect the aesthetics of the final product.
Furthermore, it is important to clean the workpiece to ensure proper adhesion of the layer. This allows the layer to develop its full protective capabilities. You can be sure of better corrosion resistance and components that can withstand the test of time.
How to Clean Aluminium Before Anodizing
The process of cleaning aluminum prior to submerging in an electrolyte solution is a detailed one. The preparation stage is as important as the anodizing operation itself as it determines the result. Follow the simple steps below to properly clean aluminum before anodizing.
Degrease
The first step in cleaning the workpiece is to remove any form of oil and grease that may have been introduced during fabrication. You carry out this step using non-etching alkaline degreasers. These degreasers are made up of surface active materials that help to emulsify and saponify oil. You apply alkaline degreasers by either spraying them or directly immersing the workpiece into the solution.
Rinsing
After degreasing, the next thing is to rinse off all residues and leftover chemicals that may be present. You rinse after the degreaser has had sufficient time to carry out its function. When rinsing, always use deionized water that doesn’t contain minerals which can interfere with the anodizing process.
Etching
Thereafter, you etch the aluminum workpiece to remove a tiny layer of the material. Here, mix the solution and carefully dip the workpiece for a predetermined period. This gives a rougher surface that increases surface area and improves adhesion. You carry out chemical etching using either acidic or alkaline solutions.
Acidic etching involves strong acids like phosphoric acid that provide a smooth and uniform finish. The use of alkaline solutions such as caustic soda is faster and more aggressive. It gives a matte and rougher finish. When etching, ensure to use the right concentration of the etching solution to get the best results.
Desmutting
Desmutting comes immediately after the chemical etching process. This step helps to remove impurities from the alloyed metals that were not dissolved by the etching solution. The most common desmut solution is 30-50% nitric acid.
When used the right way, this acid dissolves the remaining non-aluminum metals and other impurities. Note that you carry out the desmutting process at room temperature for an average of 5 minutes depending on the initial state of the workpiece and the concentration of the solution.
Rinse and Dry
The final step in preparing an aluminum workpiece for anodizing is to rinse and dry. Rinse every part with distilled or deionized water to remove all residual chemicals. Thereafter, dry it especially if there is a delay between cleaning and anodizing. You can either air dry or wipe it with a clean and soft cloth.
Precautions When Cleaning Aluminum Before Anodizing
When preparing aluminum workpieces before carrying out the anodizing process, keep the following precautions and best practices in mind.
Use Appropriate Cleaning Agents
Select the right degreasing, etching, and desmutting agents. Aluminum is highly reactive and using the wrong type of cleansers can lead to irreversible damage. When cleaning aluminum, always go for mild detergents and alkaline agents with low pH. Furthermore, use the right concentration of cleaning agents to maintain the workpiece’s integrity.
Avoid Mechanical Damage
If possible, avoid cleaning the workpiece mechanically using abrasive pads and wire brushes. Always prioritize minimally abrasive or non-abrasive tools including microfiber clothes or soft sponges. The reasons behind this are not far-fetched. Aluminum is soft and prone to scratches and dents. You can easily damage this metal if you do not handle it carefully.
Rinse Thoroughly
After every step in cleaning the aluminum workpiece prior to anodizing, ensure you rinse off residual chemicals thoroughly. When left, these chemicals can react with the anodizing bath and cause uneven layers. It may also result in discoloration and contamination of the bath. You can either submerge the workpiece in deionized water or rinse it in a continuous stream.
Protect Yourself
In everything you do, don’t forget to protect yourself. Many of these cleaning agents are hazardous and give off harmful fumes. These fumes can cause irreversible health damage such as burns, irritation, and respiratory issues. When cleaning aluminum workpieces, make sure you use the required PPEs to keep yourself safe. Additionally, ensure the workpiece is well-ventilated and dispose of the chemicals properly.
Conclusion
Anodizing is a critical aspect of aluminum part manufacturing. It unlocks the metal’s full potential and enables you to use it in various manufacturing industries. However, your approach to preparing the metal will determine how the anodizing process will go. Proper cleaning is important to ensure a stable operation and provide products that exceed customers’ expectations. Furthermore, ensure you use a reliable anodizing service provider to create high-performance and long-lasting components.
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