Aluminium in maritime environments
If aluminium is to be used in maritime environments and thus must be resistant to seawater in order to prevent corrosion, it is recommended pursuant to standard EN13195: 2009 to use a large proportion of 5000 and 6000 series alloys for maritime projects. Alloys 5083, 5754, 6060 and 6082, among other things.
For maritime aluminium structures it is recommended further, pursuant to EN1999-1-1 (Eurocode 9) to use screws, bolts and other connection elements in the material A4 316 - acid- and rustproof. If these are not used, there is risk of galvanic corrosion.
Acids and bases are damaging to aluminium
The optimal pH value for the oxide layer is in the range 4 to 9. Acids and bases break down the oxide layer, thereby opening up the raw aluminium surface. If aluminium is exposed to very strong acid or alkaline environments outside the pH range 4 to 9, violent corrosion will occur in the form of metal pitting.
Bases break down the aluminium faster than acids - for example concentrated caustic soda reacts so violently with aluminium that it can start to boil. The reaction is powerful and causes the temperature to rise, and the higher the temperature, the faster the reaction is. Thus, the reaction between aluminium and the base is self-accelerating and can accelerate violently. An example of a common alkaline material is concrete, which normally has a pH value of between 12.5 and 13.5. Concrete can therefore cause damage to the aluminium surface in the form of pitting.
As an expert in materials science and engineering, particularly in the field of metals and alloys, I bring forth a wealth of knowledge on the behavior of aluminum in maritime environments. My expertise is grounded in a comprehensive understanding of industry standards, corrosion mechanisms, and the practical applications of different aluminum alloys.
Firstly, when addressing the use of aluminum in maritime environments, it is crucial to consider the susceptibility of the material to corrosion, especially in the presence of seawater. The information provided aligns with my knowledge, as per the recommendation in standard EN13195: 2009. According to this standard, the use of 5000 and 6000 series alloys, such as 5083, 5754, 6060, and 6082, is recommended for maritime projects due to their enhanced resistance to corrosion.
Furthermore, the reference to EN1999-1-1 (Eurocode 9) underscores the importance of selecting appropriate connection elements for maritime aluminum structures. The mention of A4 316 material for screws, bolts, and other connection elements is in line with my expertise. A4 316 is known for its corrosion-resistant properties, making it suitable for use in marine environments to mitigate the risk of galvanic corrosion.
The article also delves into the impact of acids and bases on aluminum. The pH range of 4 to 9 for the optimal oxide layer aligns with my understanding of the protective nature of the oxide layer on aluminum surfaces. The explanation of how acids and bases can break down the oxide layer, leaving the aluminum vulnerable to corrosion, demonstrates a nuanced comprehension of the chemical interactions involved.
The insight into the corrosive effects of bases, particularly the example of concentrated caustic soda, adds depth to the discussion. The self-accelerating nature of the reaction between aluminum and bases, leading to violent corrosion, highlights the importance of avoiding extreme pH environments. The mention of concrete as a common alkaline material with a pH value between 12.5 and 13.5 provides practical knowledge about potential sources of damage to aluminum surfaces in maritime settings.
In conclusion, my expertise in materials science substantiates the information presented in the article, reinforcing the importance of selecting appropriate aluminum alloys and connection elements while being mindful of the corrosive effects of acids and bases in maritime environments.
