what is dissimilar metal or galvanic corrosion prevention?
Corrosion is a process of damage to a material due to environmental influences. This is a natural process in metals. Corrosion in metals and equipment in the oil and gas industry results in financial losses, pollutes the environment and can endanger human safety. Engineers and scientists do a lot of research on corrosion to prevent and control the corrosion rates.
On this occasion, we will discuss Galvanic Corrosion or known as dissimilar metal corrosion. This corrosion occurs when 2 different metal or alloy metals in the same environment and interconnected. This corrosion occurs because of the potential difference between the metals so that one metal functions as the anode and the other metal functions as the cathode. The principle of galvanic corrosion is the same as the electro-chemical principle of electrodes (cathodes and anodes), electrolytes and electric current. Metal that functions as an anode is a metal which before being connected is more active or has a more negative corrosion potential. At the anode, corrosion will occur oxidation reaction or dissolution reaction. Whereas at the cathode there is a metal reduction reaction.
Galvanic series is a list of the value of corrosion potential for various alloy metals that are useful in life. In addition, the galvanic series also lists the value of corrosion potential for pure metals. How to make galvanic corrosion prevention or dissimilar metal corrosion prevention? the simple way is to select metal pairs with very small potential differences. Please take a note, Galvanic series only provides information about the tendency for galvanic corrosion to occur in pairs of two metals or alloy metals.
Factors Affecting Galvanic Corrosion or dissimilar metal corrosion and it prevention
There are several factors that influence galvanic corrosion, including:
The degree of galvanic corrosion depends on the aggressiveness of the environment. In general, metals with lower corrosion resistance in an environment function as anodes. Galvanic corrosion does not occur if the two metals are completely dry because there are no electrolytes that move the current between the anode and the cathode.
Corrosion rates are generally greatest in the area near the meeting of the two metals. The corrosion rate decreases with increasing distance from the meeting of the two metals. The effect of this distance depends on the conductivity of the solution and galvanic corrosion can be known by the presence of local corrosion attacks in the area near the metal meeting.
3 Area of Section
If the anodic area is smaller than cathodic area, the corrosion current density will be greater. The greater the current density in the anode area, the faster the corrosion rate.
Galvanic Corrosion or dissimilar corrosion prevention
There are several common control methods for galvanic corrosion prevention or dissimilar metal corrosion prevention, which include:
- Selection of the right material. Material selection with potential differences from both materials to be as small as possible.
- Avoid the use of 2 types of metals that are interconnected in a construction.
- Using protected layers. If you have to use a protective layer, use a protective layer on the cathode.
- Avoid the combination of cross-sectional area of the material with a small anode while the cross-sectional area of a large cathode.
- Add inhibitors to reduce environmental aggressiveness.
- Design well so that you can replace damaged parts of the anode using materials that are ready to use or make thicker anodic to last longer.
that are some ways to make galvanic corrosion prevention or dissimilar metal corrosion prevention. Do you any experience of galvanic corrosion or dissimilar metal corrosion prevention? please share with us.