How to improve the corrosion resistance of Ductile Iron Parts?

1. Material selection and composition optimization

Choose ductile iron with low carbon equivalent and high magnesium content
Low carbon equivalent: Carbon equivalent refers to the sum of carbon, silicon and other elements in ductile iron. Lower carbon equivalent can reduce the precipitation of graphite, thereby improving the corrosion resistance of cast iron. Low carbon cast iron has stronger density, reduces microcracks and defects in the metal matrix, and helps to resist the invasion of external corrosive media.
High magnesium content: Magnesium is a key alloying element of ductile iron, which can promote the spheroidization of graphite, giving it higher mechanical properties and corrosion resistance. The right amount of magnesium can improve the strength, toughness and wear resistance of cast iron, and reduce its failure probability in humid or corrosive environments.
Adding alloying elements
Copper (Cu): The addition of copper can significantly enhance the corrosion resistance of Ductile Iron Parts in the atmosphere. Copper is usually used to make parts that are exposed to outdoor environments or acidic media for a long time, such as building parts, external pipes, etc. It can prevent further corrosion of the metal matrix by forming a copper oxide layer.
Nickel (Ni): Nickel increases the corrosion resistance of cast iron in chemical media, especially in seawater or acidic environments. The increase in nickel content can improve the corrosion resistance and wear resistance of ductile iron, which is suitable for marine, petroleum, chemical and other industries.
Chromium (Cr): Chromium has good antioxidant properties. It can form a passivation film on the surface of ductile iron to prevent the metal matrix from reacting with oxygen or moisture. It is widely used in high-temperature oxidizing environments. For example, ductile iron with a high chromium content has important applications in gas turbine blades or high-temperature gas processing equipment.

2. Surface treatment and coating technology

Shot Peening
Shot Peening is to use small particles of steel balls, ceramics, etc. to hit the surface of ductile iron at high speed to generate compressive stress on the surface, thereby improving the surface density and reducing the occurrence of cracks. Shot peening can effectively enhance the corrosion resistance of ductile iron, especially when used in high-stress environments, it can reduce the occurrence of fatigue corrosion and stress corrosion.
Coating Technology
Epoxy Coating: Epoxy coating is a coating with excellent chemical stability and corrosion resistance, especially suitable for hydraulic systems, pipelines and automotive parts. Epoxy coating can effectively prevent erosion by moisture, oxygen and chemicals, and extend the service life of parts.
Polyurethane Coating: Polyurethane coating has strong weather resistance and can withstand extreme weather and ultraviolet rays, so it is widely used in outdoor equipment and steel structure anti-corrosion. It can effectively protect ductile iron parts in marine or humid environments.
Metallizing: Thermal spraying technology can form a metal protective layer such as zinc or aluminum on the surface of ductile iron. This coating can form a sacrificial anode protection to prevent corrosion. This coating is particularly effective in marine environments or corrosive climate conditions.
Electroplating (such as nickel plating)
Electroplating is a method of plating metal on the surface of ductile iron through an electric current. Nickel plating can effectively improve corrosion resistance and also increase the surface finish and aesthetics. Nickel plating can provide strong protection against acidic solutions and salt spray, and is a common surface treatment method in the field of chemical corrosion resistance.

3. Surface protection treatment

Phosphating
Phosphating is a treatment method that forms a phosphate protective film on the surface of ductile iron through a chemical reaction. This treatment can not only effectively improve the surface corrosion resistance, but also increase the adhesion between the coating and the substrate, especially for cast iron parts that need to be painted. The thickness and uniformity of the phosphate film directly affect the anti-corrosion effect.
Oxidation treatment (Black Oxide)
Oxidation treatment is a common surface protection method that forms a protective film on the surface of ductile iron through oxidation reaction. The film is usually black and can provide moderate corrosion resistance. It is widely used in applications that do not require high corrosion protection but require appearance, such as tools and instrument parts.
Anodic protection
Anodic protection is a technology that uses electrochemical principles to prevent corrosion. By connecting ductile iron parts to a sacrificial anode (such as zinc or aluminum), the anode is corroded before the iron material. This technology is often used in ships, pipelines and marine engineering to reduce corrosion damage.

4. Lubrication and sealing measures

Lubricating oil film
Lubricating oil film can form a protective layer on the mechanical contact surface, isolating moisture, oxygen and corrosive media, reducing friction, wear and corrosion. For moving parts (such as ductile iron parts in hydraulic systems), lubrication is essential, especially in high temperature and high humidity environments.
High-quality seals
When designing ductile iron parts, sealing performance should be taken into consideration. High-quality seals (such as fluororubber seals) can effectively prevent the penetration of corrosive substances such as water, acid, and oil, especially in parts with more complex sealing structures. Waterproof and moisture-proof designs help maintain the corrosion resistance of parts.

5. Optimization of the use environment

Avoid long-term exposure to acid and salt environments
When designing ductile iron parts, long-term exposure should be avoided as much as possible in humid, acidic or high-salt environments. Contact with corrosion sources can be reduced through appropriate sealing design and protective measures.
Control pH value
The acidity (pH value) of industrial liquids, gases and chemicals has a great influence on the corrosion resistance of ductile iron. In liquid transportation systems, by controlling the pH value of the medium and maintaining it within an appropriate range, corrosion caused by excessive acidity or alkalinity can be effectively avoided.