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Reduction of cross-contamination during the preparation and cleaning of aluminum welds

By on September 23, 2021 0

Written by

Logbook staff

By Elliot Shepherd, Associate Product Manager, and Jerry Dillion, District Sales Manager – California, Weiler Abrasives

Aluminum is used more frequently in shipbuilding due to the many advantages offered by the material, including lighter weight and maneuverability for ships in narrower waters.

And the material is not limited to small components. It is used for many critical welds and in some cases for the construction of entire ships.

However, it is important to be aware of the common challenges of welding and cleaning aluminum and to understand how it differs from other materials. Preventing cross-contamination when preparing aluminum welds is especially critical, as cross-contamination can lead to rework or failed welds that can end up costing thousands or even millions of dollars.

Choosing the right product for weld preparation and cleaning can help reduce the risk of cross-contamination when welding aluminum.

How does cross contamination occur?

Aluminum welds are generally more susceptible to contamination than other materials. It is therefore crucial to thoroughly clean the aluminum base metal before welding to remove any contaminants or impurities that may be on the material. This ensures good penetration and a good final weld.

Cross contamination can occur in many ways, including from other metals. Contamination can also occur if elements such as sulfur, iron or chlorine are introduced. This type of contamination can be introduced in several ways.

  • Contamination of the environment or storage in the installation: When aluminum is stored, prepared and welded in the same facility where carbon steel or other metals are also stored, prepared and welded, it can lead to cross contamination. Grinding carbon steel throws 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 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 arise when a ceramic grinding wheel is used first on steel and then on aluminum. Although operations may try to limit the number of products they use, it is recommended to use aluminum cutting and grinding wheels for aluminum and steel products for steel, and never to mix the two. This limits the potential for cross contamination.

The ramifications of poor weld cleaning or using the wrong product on aluminum can be significant and can occur weeks or months later. When faulty welds or cracked seams are discovered, they may require extensive rework.

If the ship is not yet finished when errors are detected, it can also cause delays in the project. If the vessel is already in service, failed welds caused by cross-contamination can be even more costly, possibly requiring a complete rebuild of the vessel with a multi-million dollar price tag. The blackouts could also be catastrophic if they happen when the ship is in the middle of the ocean.

Prevention of cross contamination

Many shipbuilding operations have strict guidelines regarding the types of surface conditioning products that can be used in the facility.

Large operations often have a tool room where they store abrasives. Installations dedicated solely to welding aluminum have much less potential for cross-contamination. In facilities where many types of materials are stored, prepared and welded, care must be taken to keep the materials separate. A good way to avoid cross-contamination is to store aluminum-specific abrasives in their own sealed and airtight containers.

In a situation where cross contamination has occurred (or the operator believes it may have occurred), thoroughly clean the base material with a solvent to remove contamination from the surface.

Choosing the right abrasives for aluminum

One of the primary ways to avoid cross-contamination when preparing or cleaning aluminum welds is to choose abrasives specifically designed for use with aluminum. Abrasives manufacturers have tested these products and designed them not to leave contaminants on the aluminum.

For cleaning before welding, such as removing corrosion or oxide from the workpiece, it is recommended to use a stainless steel wire brush. Wire brushes also eliminate product loading issues as there are no abrasive grains that aluminum can adhere to. Charging occurs when the base material heats up and adheres to the abrasive grains, clogging them.

Cutting and grinding aluminum often requires the use of bonded abrasives. Aluminum specific products work great because they are formulated to work more smoothly and minimize load during the process. Coated abrasives specially designed for aluminum can also be used.

Many bonded and coated abrasives designed for aluminum have an additive or topcoat that makes it easier to grind the aluminum while minimizing the load. This improves productivity and prolongs the life of the product.

Preparation and cleaning of aluminum welds

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 touch-ups.

The use of abrasives suitable for aluminum ensures the necessary quality, avoids rework and improves productivity and efficiency. While abrasives designed specifically for aluminum may cost more upfront, they save time and money in the long run.

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