Specifications and Models of Aluminum Alloy Sacrificial Anodes for Cathodic Protection in Ballast Tanks

Specifications and Models of Aluminum Alloy Sacrificial Anodes for Cathodic Protection in Ballast Tanks

The sacrificial anode method is a common anti-corrosion technique.
Aluminum alloy anodes are blocks used for anti-corrosion purposes.
For example, when attached to a pipe, the anode corrodes while the iron does not. Because aluminum has a more negative electrode potential than iron, it protects the pipe from corrosion. This method is called sacrificial anode protection, with the aluminum alloy serving as the sacrificed anode.

Introduction to Aluminum:

Color and state: Silvery-white metal
Atomic radius: 1.82
Common valence: +3
Discoverers: Ørsted, Wöhler
Discovery time and place: 1825, Denmark
Source: The most abundant metal in the Earth's crust, accounting for over 7%
Uses: Structural material. Pure aluminum is used for ultra-high voltage cables. Aluminum for daily utensils is often called "aluminum ware" or "aluminum alloy."
Industrial production method: Electrolysis of a mixture of molten alumina and cryolite
Laboratory production method: Electrolysis of molten aluminum chloride
Other compounds: AlCl3 - Aluminum chloride, NaAlO2 - Sodium aluminate, Al(OH)3 - Aluminum hydroxide
Extended introduction: A bluish silvery-white trivalent metal with good ductility, toughness, and the ability to produce a [resonant] sound. It is renowned for its light weight, excellent electrical and thermal conductivity, high reflectivity, and oxidation resistance.
Discoverer: Wöhler
Discovery year: 1827

Introduction to Aluminum Alloy Sacrificial Anodes:
Exceptional electrochemical performance, high power output per unit weight of anode material, approximately three times that of zinc anodes and twice that of magnesium anodes. Performs well in seawater and other media containing chloride ions, with strong self-regulating current output capability. Suitable for cathodic protection against metal corrosion in seawater environments for ships, mechanical equipment, marine engineering, port facilities, as well as pipelines and cables in seabed mud.

Application Scope of Aluminum Alloy Sacrificial Anodes: Aluminum alloy sacrificial anodes are suitable for cathodic protection against metal corrosion in seawater environments for ships, mechanical equipment, marine engineering, port facilities, as well as pipelines and cables in seabed mud.

Hello: Aluminum alloy sacrificial anodes are suitable for cathodic protection against metal corrosion in seawater environments for ships, mechanical equipment, marine engineering, port facilities, as well as pipelines and cables in seabed mud. The most commonly used aluminum alloy anodes are Al-Zn-In series and Al-Zn-Hg series anodes. The production of aluminum alloy anodes complies with the GB4948-2002 standard for "Al-Zn-In Series Alloy Sacrificial Anodes."
Aluminum alloy sacrificial anodes refer to alloys primarily composed of aluminum, used for protecting cathode engineering, hence termed aluminum alloy sacrificial anodes. The most commonly used aluminum alloy sacrificial anodes today are Al-Zn-In series and Al-Zn-Hg series anodes, suitable for cathodic protection of structures such as buried oil and gas pipelines, ships in seawater, port and marine facilities, seawater cooling systems, and storage tank sediment water areas. The production of aluminum alloy anodes complies with the GB4948-2002 standard for "Al-Zn-In Series Alloy Sacrificial Anodes."
Aluminum alloy sacrificial anodes exhibit exceptional electrochemical performance, high power output per unit weight of anode material, approximately three times that of zinc anodes and twice that of magnesium anodes. They perform well in seawater and other media containing chloride ions, with strong self-regulating current output capability.

What is Required for Aluminum Anodizing?

The composition of the anodizing solution and process conditions are as follows:

Name Content (ml/L)

Sulfuric Acid (H2SO4) 100–200

Voltage/V 12

Anodizing Time/min 20–120

Power Supply DC

Cathode-to-Anode Area Ratio 1.5

Temperature/°C 20–30

Average Current Density/A•dm⁻² 0.10

1) When the sulfuric acid (H2SO4) solution concentration is higher, the resulting film is easier to color, with deeper colors and higher porosity. When the sulfuric acid (H2SO4) solution concentration is lower, coloring is slower, with lighter colors and lower porosity. Therefore, to produce a film with strong adsorption and elasticity, a higher concentration anodizing solution can be used. For a hard and wear-resistant oxide film, a lower concentration anodizing solution is preferable.

2) During anodizing, the initial current density greatly affects the structure of the oxide film. Excessively high current density can cause the edges of the specimen to burn, resulting in a very rough oxide film. Therefore, during anodizing, the current density should be gradually increased to a certain value, and voltage fluctuations should ideally not exceed 2V thereafter. When the current density exceeds 3.3 A•dm⁻², the corrosion resistance of the oxide film decreases with increasing current density. However, when the current density does not exceed 3.3 A•dm⁻², increasing current density increases porosity, making the film easier to dye and improving corrosion resistance.

3) Within one hour, the growth of the oxide film is proportional to the anodizing time. However, if the anodizing time is too long, the surface of the oxide film dissolves in the electrolyte, gradually increasing pore size and making the film layer rougher.

Electrode potential of magnesium: -2.375V
Electrode potential of aluminum: -1.706V
Electrode potential of zinc: -0.763V
Electrode potential of iron: -0.409V
Electrode potential of copper: +0.340V
For zinc-aluminum alloys, the higher value of -0.763V must be considered. Thus, if zinc-aluminum alloy is used as a sacrificial anode, it can protect metals like iron and copper but cannot protect magnesium.
Currently, the main anodes are magnesium, aluminum, and zinc. Magnesium alloys are used in soil, zinc alloys in seawater, and aluminum alloys in freshwater.