By Elliot Shepherd, associate product manager, and Jerry Dillion, district sales manager – California, Weiler Abrasives
Aluminum is being used more frequently in shipbuilding thanks to the many benefits the material offers, including lighter weight and maneuverability for ships in tighter waters.
And the material isn’t limited to small components. It’s used for many critical welds and—in some cases—for constructing entire ships.
However, it’s important to be aware of common challenges involved with welding and cleaning aluminum and understand how it differs from other materials. Preventing cross-contamination when preparing aluminum welds is especially critical, as cross-contamination can result in rework or failed welds that may end up costing thousands or even millions of dollars.
Choosing the right product for weld prep and cleaning can help reduce the chance for cross-contamination in aluminum welding.
How Does Cross-Contamination Happen?
Aluminum welds are typically more susceptible to contamination than other materials. This makes it crucial to thoroughly clean the aluminum base metal before welding to remove any contaminants or impurities that might be on the material. This helps ensure proper penetration and a good final weld.
Cross-contamination can happen in multiple ways, including from other metals. Contamination can also happen if elements such as sulfur, iron or chlorine are introduced. This type of contamination can be introduced in several ways.
- Environmental or storage contamination in the facility: When aluminum is being stored, prepared and welded in the same facility where carbon steel or other metals are also being stored, prepared and welded, it can result in cross-contamination. Grinding carbon steel puts microscopic iron particles into the air that can settle as dust. If this dust lands on the aluminum base material or filler metals, it can cause rust on the material very quickly.
- Using the wrong abrasive: The abrasive product used to grind or clean the metal can also be a source of cross-contamination if an operator uses the wrong product for the material. For example, a steel wire wheel used on aluminum or a bonded abrasive that is not labeled as contaminant-free are common sources of cross-contamination on aluminum. The problem can also occur when a ceramic grinding or cutting wheel is first used on steel and then on aluminum. While operations are likely to try to limit the number of products they use, it’s recommended to use aluminum cutting and grinding wheels for aluminum and steel products for steel—and never mix the two. This limits the potential for cross-contamination.
The ramifications of improper weld cleaning or using the wrong product on aluminum can be substantial—and they could occur weeks or months down the road. When failed welds or cracked seams are discovered, they may require significant rework.
If the ship is not yet completed when mistakes are found, it can also mean project delays. If the ship is already in service, failed welds caused by cross-contamination can be even more costly—perhaps requiring an entire ship rebuild with a price tag of millions of dollars. Failures could also be catastrophic if they occur when the ship is in the middle of the ocean.
Many shipbuilding operations have stringent guidelines regarding what types of surface conditioning products can be used in the facility.
Larger operations often have a tool room where they store abrasive products. Facilities that are dedicated to only aluminum welding have much less potential for cross-contamination. In facilities where many material types of stored, prepared and welded, it requires diligence to keep the materials separated. One good way to prevent cross-contamination is to store aluminum-specific abrasives in their own sealed, air-tight containers.
In a situation where cross-contamination has happened (or the operator believes it may have happened), clean the base material thoroughly with a solvent to remove the contamination from the surface.
Choosing Proper Abrasives for Aluminum
A primary way to prevent cross-contamination when preparing or cleaning aluminum welds is to choose abrasive products that are made specifically for use with aluminum. Abrasives manufacturers have tested these products and designed them to not leave contaminants on aluminum.
For pre-weld cleaning, such as removing corrosion or oxide from the work piece, it’s recommended to use a stainless steel wire brush. Wire brushes also eliminate concerns about product loading since there are no abrasive grains for the aluminum to stick to. Loading occurs when the base material heats up and adheres to the abrasive grains, clogging them up.
Cutting and grinding aluminum often requires the use of bonded abrasives. Aluminum-specific products work very well because they are formulated to run more smoothly and minimize loading during the process. Coated abrasives designed specifically for aluminum can also be used.
Many bonded and coated abrasives designed for aluminum have an additive or topcoat that aids in grinding aluminum while minimizing loading. This helps improve productivity and extend product life.
Aluminum Weld Prep and Cleaning
The use of aluminum is growing in many industries—including shipbuilding. Taking the proper steps and following best practices when preparing and cleaning aluminum can help save time and money and eliminate the potential for costly rework.
Using the proper abrasives for aluminum helps ensure the necessary quality, prevent rework and benefit productivity and efficiency. While abrasive products designed specifically for aluminum may cost more upfront, they save significant time and money in the long run.