02-24-2018, 03:32 AM
most industries, the standard recommendation is to store aluminum inside prior to fabrication. While that is a good recommendation, it probably is unrealistic in the shipbuilding industry, where most welding is performed outside. There are more realistic storage recommendations for shipbuilding.
First, if at all possible, do not stack the aluminum plates in a flat stack on the ground. Storage in this way traps water between the sheets, increasing corrosion rates. Instead, stack the plates on edge to allow water to drain between the pieces. If sheets must be stacked flat, remove any paper interleaving or packing from between the plates. If left in place, the paper will act as a wick and draw water into between the plates. If the sheets are stacked flat, try not to stack one sheet directly on top of another. Instead, insert small wood or aluminum “stickers” between the sheets to let water drain.
All of this is intended to minimize the amount of corrosion, i.e., thick oxide that can form between the stored sheets. Any thick oxides will need to be mechanically removed before welding.
Make Sure You Clean the Parts Adequately Before Welding
Cleaning aluminum before welding consists of two separate and distinct operations. First, all oils, lubricants, machining coolants and other hydrocarbons used in manufacturing must be removed. Any hydrocarbons remaining on the material will get into the welding arc and release hydrogen gas, which causes weld porosity.
Removing hydrocarbons can be done in one of two ways. The most common is to wipe the plate with a clean rag saturated with a good degreasing solvent, such as acetone, toluene, MEK or carburetion cleaner. (Alcohols are not good degreasers and should not be used to clean aluminum.) Alternatively, but less common, the aluminum can be dipped into a tank containing a mild alkaline solution, then rinsed and dried.
Secondly, remove any heavy oxides from the aluminum before welding. This is normally done by hand or mechanically using a stainless steel wire brush. In cases where the materials are stored outside and develop a heavy gray oxide, it may be necessary to remove the oxide using a sanding or grinding disk.
First, if at all possible, do not stack the aluminum plates in a flat stack on the ground. Storage in this way traps water between the sheets, increasing corrosion rates. Instead, stack the plates on edge to allow water to drain between the pieces. If sheets must be stacked flat, remove any paper interleaving or packing from between the plates. If left in place, the paper will act as a wick and draw water into between the plates. If the sheets are stacked flat, try not to stack one sheet directly on top of another. Instead, insert small wood or aluminum “stickers” between the sheets to let water drain.
All of this is intended to minimize the amount of corrosion, i.e., thick oxide that can form between the stored sheets. Any thick oxides will need to be mechanically removed before welding.
Make Sure You Clean the Parts Adequately Before Welding
Cleaning aluminum before welding consists of two separate and distinct operations. First, all oils, lubricants, machining coolants and other hydrocarbons used in manufacturing must be removed. Any hydrocarbons remaining on the material will get into the welding arc and release hydrogen gas, which causes weld porosity.
Removing hydrocarbons can be done in one of two ways. The most common is to wipe the plate with a clean rag saturated with a good degreasing solvent, such as acetone, toluene, MEK or carburetion cleaner. (Alcohols are not good degreasers and should not be used to clean aluminum.) Alternatively, but less common, the aluminum can be dipped into a tank containing a mild alkaline solution, then rinsed and dried.
Secondly, remove any heavy oxides from the aluminum before welding. This is normally done by hand or mechanically using a stainless steel wire brush. In cases where the materials are stored outside and develop a heavy gray oxide, it may be necessary to remove the oxide using a sanding or grinding disk.