This document discusses corrosion of ductile cast iron. It defines corrosion and describes common types like rust and galvanic corrosion. Factors that affect corrosion rates are outlined. Corrosion testing methods for ductile cast iron are then explained, including weight loss tests and salt spray testing. Example calculations of corrosion rate are shown. Test results are displayed in a table comparing corrosion rates of ductile cast iron in MgSO4 and NaCl solutions over various time periods.

1. MANIKANDAN K
DEPARTMENT OF MECHANICAL ENGINEERING
EASA COLLEGE OF ENGINEERING AND TECHNOLOGY

2. Cast iron
Cast iron, is an alloy of iron, that contains 2 to 4 percent carbon,
along with varying amounts of silicon and manganese and traces of
impurities such as sulfur and phosphorus.

3. CAST IRON DUCTILE CAST IRON
Cast iron is an alloy of iron that we
can readily cast in a mould.
Ductile iron is an alloy of iron, which is
rich with graphite
Contains iron, carbon, silicon,
manganese along with trace amounts
of sulfur and phosphorous
Contains iron, carbon, silicon, manganese
magnesium, etc. Along with copper or tin
Contains 2 to 4% carbon Contains 3.2 to 3.6% carbon
Silicon contents are 1 – 3% Silicon contents are 2.5%
High ductility Less ductility
Cookware, Bridge Components,
Machinery Bases, Manhole Covers
Pipes, Machines And Automotive Industry
Parts, Such As Cylinder Heads, Cylinder .
Definition
Composition
Carbon
Silicon
Ductility
Applications

5. TYPES OF CORROSION
Rust: Rust is a type of corrosion that specifically affects
iron and steel. It forms when iron reacts with oxygen and
moisture to produce iron oxide (Fe2O3), which is a reddish-
brown, flaky substance.
Galvanic Corrosion: This occurs when two dissimilar
metals come into contact in the presence of an electrolyte
(e.g., moisture). The more reactive metal corrodes more
quickly.

6. PITTING CORROSION: Pitting corrosion is characterized
or pits in the metal surface. It is particularly damaging because it can lead to structural
failure.
UNIFORM CORROSION: This type of corrosion
of the material, resulting in a general thinning of the metal.

7. Factor Affecting Corrosion
Environmental Conditions: Moisture,
oxygen, and the presence of corrosive
substances like salts or acids can accelerate
corrosion.
Temperature: Elevated temperatures can
often accelerate the rate of corrosion.

8. Metallurgical Factors: The composition and structure of the metal can
influence its susceptibility to corrosion. Some alloys and coatings are
more corrosion-resistant than pure metals.
Surface Condition: Surface defects, , or roughness
sites for corrosion
Electrolytes: The presence of electrolytes, , can
enhance the corrosive process.

9. Corrosion Is Not Just A Matter Of Durability As It
Can Directly Affect The Mechanical And Structural
Properties Of Components And The Global
Response Of The Structure.
Mechanical Damage Of Pipes
Loss Of Mechanical Properties (E.G. On Metallic
Bridges)
Loss Of Efficiency
Pollution Due To Release Of Particles From
Corrosion
EFFECT OF CORROSION

10. Corrosion testing can help to predict materials resistance to
corrosion to esteem component life-cycle, compare
different materials and assess a material’s behavior in a
particularly corrosive environment. Corrosion testing can
also help producers to understand if the coating processes
are being performed to specification.
CORROSION TESTING

11. Types Of Corrosion Tests Can Be Conducted On
Ductile Cast Iron To Evaluate Its Resistance To
Different Corrosive Environments
Weight Loss Test: This Is A Basic And Widely Used
Corrosion Test. It Involves Immersing The Ductile
Cast Iron Specimen In A Corrosive Solution For A
Specific Period And Then Measuring The Weight
Loss. The Corrosion Rate Can Be Calculated Based
On The Weight Loss Over Time.
Salt Spray Test (Astm B117): In This Test, The
Ductile Cast Iron Samples Are Exposed To A
Saltwater Mist To Simulate Salt-laden Environments,
Such As Coastal Areas. This Test Helps Assess The
Material's Resistance To Atmospheric Corrosion.

12. Immersion Tests:
These tests involve immersing ductile cast
iron samples in various corrosive solutions,
including acids, alkalis, or specific industrial
environments, to evaluate how the material
reacts over time.

13. 1. Sample Preparation:
2. Preparation of Corrosive Solution:
3. Initial weight measuring
4. Exposure to Corrosive Environment/ Immersion
5. Monitoring
6. Removal and Cleaning
7. Final weight measuring
8. Corrosion Rate Calculation:

14. MODEL CALCULATIONS:
WEIGHT LOSS
ΔW = Wi – Wf
= 42.78 – 42.768
ΔW= 0.012grm
Where:
ΔW = Weight loss (in grams)
Wi = Initial weight of the specimen (in grams)
Wf = Final weight of the specimen after exposure (in
grams)

15. Where,
CORROSION RATE:
(CR) = (ΔW / A) / (ρ × t)
= (0.012/598)/(7.15x24)
(CR) = 33.6086
Where,
ΔW = weight changes in gms
A = Area in mm2
ρ =density in g/cm3
t = time in hrs

16. Corrosion rate of MgSO4 Corrosion rate of NaCl
33.6086 33.6086
11.7828 23.5657
13.6114 27.2228
20.7360 5.1840
26.6811 3.8116
CORROSION RATE DEPENDS UPON DIFFERENT SALT

17. 24 72 120 168 216
MgSO4 33.6086 11.7828 13.6114 20.736 26.6811
NaCl 33.6086 23.5657 27.2228 5.184 3.8116
33.6086
11.7828
13.6114
20.736
26.6811
33.6086
23.5657
27.2228
5.184
3.8116
CR
in
mpy
TIME in hrs
Corrosion rates of MgSO4 & NaCl
MgSO4
NaCl

18. Conclusion
This study aims to provide valuable insights into the corrosion
resistance of ductile cast iron in these specific salt environments,
helping to determine the material's suitability for applications where
exposure to such conditions is common.