High-Quality Tank Aluminum Alloy Sacrificial Anode

High-Quality Tank Aluminum Alloy Sacrificial Anode

The inner walls of tanks are mostly protected using block-shaped aluminum alloy sacrificial anodes, which are directly welded to the inner surface of the tank bottom. Aluminum alloy block anodes are precious metals and do not have any paint or coating on their surface. The protection principle is based on the electrolytic cell mechanism, ensuring no impact on the quality of the oil product.
When the sacrificial anode material on the inner wall is depleted, it needs to be replenished, which requires tank cleaning. Typically, the design protection life for the inner wall exceeds ten years, though the actual duration depends on the design usage. In the short term, this aspect may not need consideration. If sacrificial anode cathodic protection is already installed outside the tank, will adding sacrificial anode cathodic protection at the tank bottom cause interference?
No interference will occur because they are not insulated from each other. Adding sacrificial anodes merely compensates for the protective current. There is no interference since the current magnitude and direction remain consistent; it simply increases the current in the parallel path.

How to Implement Effective Tank Cathodic Protection:

1、Sacrificial anode cathodic protection involves connecting a metal with a more negative potential to the protected metal within the same electrolyte, transferring electrons from the anode to the protected metal. This ensures the entire protected metal attains a uniformly negative potential. This method is simple, requires no external power source, and rarely causes corrosion interference. It is widely used for protecting small structures (current generally less than 1 ampere) or metal structures in low soil resistivity environments (soil resistivity less than 100 ohm-meters), such as urban pipelines and small tanks. According to domestic reports, there have been many failures with sacrificial anodes, with their service life typically not exceeding 3 years and at most 5 years. The main reason for failure is the formation of a non-conductive hard layer on the anode surface, limiting current output. The primary cause of this issue is the anode composition not meeting specifications, followed by high soil resistivity at the anode location. Therefore, when designing a sacrificial anode cathodic protection system, it is essential to strictly control anode composition and select anode bed locations with low soil resistivity.
2、Impressed current cathodic protection uses an external DC power source and auxiliary anodes to force current from the soil to the protected metal, lowering the potential of the metal structure below that of the surrounding environment. This method is mainly used for protecting large structures or those in high soil resistivity environments, such as long-distance buried pipelines and large tank groups.

3、Cathodic protection is divided into sacrificial anode and impressed current methods. Tank cathodic protection is no exception and can use either sacrificial anodes or impressed current.
Using sacrificial anodes for tank protection involves the issue of shorter service life. Once the anodes are consumed, replacement is cumbersome, requiring breaking the hardened ground around the tank to re-bury the sacrificial anodes. Therefore, impressed current is generally used for tank cathodic protection. The anode bed material typically consists of MMO precious metal ribbon anodes or flexible anodes.

Tank Cathodic Protection Potential High-Quality Tank Aluminum Alloy Sacrificial Anode

Tanks generally use impressed current cathodic protection. After construction is completed, the tank potential can be displayed on the constant potential instrument display cabinet. The principle is similar to that for pipelines: one cable connects to the tank, and another connects to a reference electrode buried around the tank, allowing measurement of the tank potential. High-Quality Tank Aluminum Alloy Sacrificial Anode

Potential measurement essentially measures the potential difference between the protected metal and the reference electrode. Since the reference electrode's potential is assumed constant, any change in the measured current is interpreted as a change in the structure's potential. However, this may not always be accurate, as the reference electrode's potential could also change. Factors affecting reference electrodes include: Temperature effects: Increased temperature can alter solution concentration, causing changes in the reference electrode potential and affecting its linearity. For common copper/copper sulfate reference electrodes, the temperature influence is approximately 0.9 mV/°C. For instance, at around 26°C, the measured pipeline potential should be -0.85 V, while at about 5°C, it may be around -0.825 V. Therefore, when measuring crude oil tanks, the impact of crude oil heating should be considered. For portable reference electrodes, solar exposure can cause potential changes of about 10 millivolts. To minimize this, wrapping the electrode with black tape can help. Changes in the tank bottom plate can also affect measured potential. For example, heating crude oil may cause the bottom plate to deform and bulge. When the plate warps, some areas may lose contact with the tank foundation, receiving insufficient protective current and leading to polarization. To avoid inaccurate measurements due to this phenomenon, maintain the tank liquid level at about 2/3 for a certain period during measurement. Jiaozuo Libo Light Alloy Co., Ltd. supplies high-quality tank aluminum alloy sacrificial anodes from Jiaozuo Libo Light Alloy Co., Ltd.