Galvanic corrosion ruins design and longevity. This is a slightly different type of corrosion in terms of how it affects a construction site or a particular metallic structure. Aluminum and steel are the most common ones which get affected by galvanic corrosion.
To know how to prevent galvanic corrosion between aluminum and steel, you must go through the article. We are about to provide 4 prevention techniques.
First, we need to know what galvanic corrosion is. It’s also named bimetallic corrosion. An electrochemical process occurs if two different types of metals are connected by an electrolytic means (mostly saltwater). Here, the cathode (one metal) remains protected, and the other one gets corroded.
What Is Galvanic Corrosion?
Galvanic corrosion is special corrosion that requires electrolytic solutions and two immersed metals. The electrolytic solution works as the catalyst to corrode the anode, and the cathode metal remains the same.
Bimetallic corrosion or galvanic corrosion hampers construction’s design, stability, and durability. Steel, one of the major ingredients for buildings, comes across as aluminum, another common metal for construction sites.
When both are immersed in a chloride solution or electrolyte without any insulation, the aluminum will keep transferring electrons to steel. The result of such transferring process is weakened aluminum construction.
Where Does Galvanic Corrosion Occur?
We’ve already stated that a connecting electrolyte requires galvanic corrosion to occur. Rainwater, saltwater, and marine environment are mostly the common places where galvanic corrosion takes place.
If you’re building a ship and need to use both steel (carbon) and aluminum, the saltwater will transfer aluminum’s electrons to carbon. What will happen then? You’ll end up with corroded aluminum sheets that are weak, less durable, and inappropriate for building a strong site.
And, this is the reason you know the prevention process.
How to Prevent Galvanic Corrosion Between Aluminum and Steel
Two structurally dissimilar metals connected through electrolytes get into an electrochemical process that is known as bimetallic corrosion. Thereby, the prevention is related to create an obstacle within the process.
- Insulation
If you give close attention to the process of galvanic corrosion, you’ll know how insulation will prevent it. Electrons run from anode to cathode or aluminum to steel, right? What if you put insulation between the anode and cathode? No more corrosion will take place.
The most available insulation materials are polymer and elastomer-based. By putting an insulating cover or coating around the aluminum or steel, galvanic corrosion is preventable.
For example, many firms and marine construction manufacturers use GRE (glass-reinforced epoxy) as an insulation compound. Gaskets made of GRE prevent galvanic corrosion by keeping both aluminum and steel separate.
- Isolation
One of the main reasons behind causing bimetallic corrosion is the electrolyte. If you can isolate electrolyte or reduce its oxidation or reduction capacity, the bridge will be broken.
How can you exactly break the bridge? By using painting, it is possible to prevent the electrolyte from transferring electrons and weakening aluminum.
Large construction sites such as mining stations and offshore drilling sites are painted properly to isolate the electrolyte. This is also a cost-effective concept for reducing the risk of galvanic corrosion.
- Inhibitors
Another method to prevent galvanic corrosion is to add inhibitors for reducing the capacity of electron transfer. There are several liquid corrosion inhibitors found in the market.
These protect both aluminum and steel from being involved in the electrochemical process. Corrosion inhibitors are mostly used in small areas and sites to make them cost-effective.
The inhibitor removes oxygen from the electrolyte solution to inhibit electrolytes from performing the oxidation and reduction process. If there’s no oxygen, there’ll be no oxidation or reduction. As simple as that to prevent galvanic corrosion between aluminum and steel.
- Area ratio
The cathode and anode’s area ratios are highly impacting factors for galvanic corrosion. If the cathode area is larger than the anode area, the anode or aluminum will get corroded at a quick pace.
By turning the area ratio to the opposite, aluminum will not get corroded easily. To minimize the area ratio, you’ll have to identify the exact portion that both remain in their best condition.
FAQs
We get frequent questions regarding the prevention techniques of galvanic corrosion. Find frequently asked questions here:
1. Does galvanic corrosion require water?
Answer: Galvanic corrosion occurs by using oxidation and reduction between two metals such as steel and aluminum with an electrolyte media. And, this electrolyte solution requires oxygen for sure. Water is a mandatory element to develop the connection between aluminum and steel.
2. Can stainless steel be corroded?
Answer: Stainless steel is free from stains; but not from corrosion. If the stainless steel is exposed to different conditions such as saltwater or rainwater and comes across aluminum, it will get corroded.
3. How can coating prevent galvanic corrosion?
Answer: Certain factors, including coating, can prevent galvanic corrosion from happening. By applying proper coating on anode and cathode, electrons cannot be exchanged. As a result, it prevents galvanic corrosion.
However, you need to choose the coating material carefully. Otherwise, corrosion may occur at a fast pace.
4. Does saltwater quicken bimetallic corrosion?
Answer: Saltwater includes sodium, chlorine, and other compounds. Saline water or saltwater works effectively as an electrolyte. If steel and aluminum are immersed into saltwater, it quickens bimetallic corrosion.
Not only saltwater but also rainwater has electrolyte characteristics. When preventing, steel and aluminum should not be connected through any of these.
Bottom Line
Both aluminum and steel are important for day-to-day construction. Getting exposed to certain environments introduces these two elements to corrosion. Galvanic corrosion must be prevented to save aluminum from getting weakened.
All the four processes discussed in the article regarding preventing galvanic corrosion between aluminum and steel are easy and cost-effective. If you encounter any issue of bimetallic or galvanic corrosion, try to apply any of the methods.
When you coat steel and aluminum and put a bridge or inhibitor, it’ll be easy to prevent galvanic corrosion.