The Best Cleaning Methods and Chemistries for Aluminum

Executive Summary

Overview: Aluminum is a versatile yet sensitive metal susceptible to etching, pitting, “smutting,” and cavitation erosion when exposed to harsh chemicals or improper ultrasonic frequencies. Choosing the correct cleaning chemistry and process is critical to preventing surface damage and costly part rejections in high-stakes industries like aerospace, medical device, and semiconductor manufacturing.

Key Takeaways:

• Chemistry Selection: Avoid strong acids and high-alkaline solutions (pH > 9). Opt for neutral aqueous cleaners (pH 6–9) or specially inhibited formulas (e.g., JAYCO JC-201C, JC-301SC) to protect sensitive alloys such as 7075 and 5080.
• Ultrasonic Parameters: Use higher ultrasonic frequencies (40 kHz to 430 kHz) with gentle vertical agitation to eliminate cavitation erosion caused by harsh, low-frequency imploding bubbles.
• Rinsing & Drying: Rinse with Deionized (DI) or Reverse Osmosis (RO) water and dry immediately to eliminate hard-water spots, film residues, and trapped water corrosion.

Aluminum is a soft, lightweight, and robust metal. Because of this, it’s more easily damaged during the cleaning process if managed incorrectly. 

The surface of aluminum cannot withstand many harsh chemicals or abrasions, and it can react poorly to certain solutions. Manufacturers should be aware of the properties of their cleaning products prior to cleaning in order to prevent corrosion or other surface damage.

There are a variety of ways to clean aluminum, including:

• Aqueous Cleaning: Spray washers and cabinet washers spray heated water and particular chemical solutions onto the aluminum surface to get rid of contaminants like coolants or oils that are left behind during the manufacturing process. 
• Ultrasonic Cleaning: With the ultrasonic cleaning method, aluminum parts are submerged in a liquid bath, and high-frequency sound waves create cavitation bubbles. As the bubbles hit the surface of the aluminum, they “scrub” away leftover solutions from hard-to-reach nooks and crannies without damaging the surface.

Rinsing and Drying

Tap water that contains minerals can leave white spots on aluminum when water evaporates. Because of this, once an aluminum part is washed, it is often rinsed with deionized or reverse osmosis water. This prevents any contamination that would affect the part in the next stage of operation. 

Parts must be quickly and fully dried for optimal results. Leaving water trapped in a hard-to-reach place on a part can cause corrosion.

What Manufacturers Should Watch Out For

Etching, Pitting, and “Smutting”

Aluminum is “amphoteric,” meaning it reacts poorly to both strong acids and strong bases. Because aluminum is highly sensitive to high-pH chemicals, high-alkaline cleaners can cause excessive etching and pitting. 

Etching and pitting can happen by selectively dissolving the aluminium metal with the chemical solution or small localized electrochemical corrosion sites forming.  Etching can also leave behind a gray or black metallic soot residue known as “smut” that cannot simply be rinsed off with water. 

–> To avoid this, use 301SC, which will protect your aluminum surface.

Ultrasonic Cavitation Erosion

It’s important to use the proper ultrasonic frequencies during cleaning. Lower ultrasonic frequencies such as 25kHz produce massive imploding bubbles that are better for heavy steel. But with soft aluminum, these bubbles can cause cavitation erosion on the aluminum surface finish.

→ To avoid this, use higher ultrasonic frequencies (40 kHz to 430 kHz) to generate smaller cavitation bubbles paired with JC 300C. In addition, moving the part through the bath slowly with vertical agitation can help reduce the cavitation erosion.

Chemical Residue, Staining, and Film Build-Up

For aluminum parts that will be used in highly sensitive situations, particularly in the aerospace or medical industries, strong chemicals pose a risk for corrosion, staining, or other reactions. This commonly occurs when only light residues or microscopic organic contaminants need to be removed but heavy-duty cleaners are used and are overly harsh on the metal.

Even though it is best practice to use a mild approach to protect sensitive aluminum, “safe” cleaners can lack the chemical strength to break down heavy-duty soils. They can also leave behind chemical films and residues that interfere with downstream processing and compliance, like silicate-inhibited cleaners can.

→ To avoid this, use a neutral aqueous cleaner with a pH between 6 and 9 such as JC 205C or JC 201C. These milder formulas are safe for aluminum surfaces and can gently remove minor soiling without aggressively attacking the surface and leaving behind damage or staining.

When 7075 aluminum is cleaned improperly, dark spots or streaks can appear on its surface. These markings are not simply a cosmetic issue. In the aerospace industry, and many other high stakes industries, surface imperfections like dark spots and streaks cause parts to be rejected.

The 5080 series aluminum is used in semiconductor chip manufacturing equipment, particularly in vacuums and equipment bodies. This aluminum is another alloy that is sensitive to higher alkaline cleaners and can be damaged by them. 

→ Jayco’s JC 201C has been specifically formulated to clean these alloys properly and sensitively. 

Water Corrosion

When heavy-duty greases, oils, and lubricants are leftover from manufacturing and caught in hard-to-reach crevices, liquid cleaning methods are necessary to dissolve the residue completely. Traditionally, some complex aluminum parts haven’t tolerated water-based washing methods. 

Tap water can contain harsh minerals that affect the aluminum’s surface, leaving undesirable and non-compliant white spots. Water can also get trapped during the washing process, causing corrosion. 

→ To avoid these issues it’s important to use cleaners with the right inhibitors like JAYCO’s JC 201C. Rinsing parts with Deionized (DI) water or Reverse Osmosis (RO) water also helps to ensure zero chemical drag-over from the cleaning process and prevents hard water spots. 

For more information on the right aluminum chemistries and methods for your process, reach out to our team at JAYCO for assistance.

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