Corrosion resistant materials are selected in engineering to prevent material degradation when exposed to water, air, chemicals or harsh environments. Choosing the correct material is critical to ensuring long service life, safety and reduced maintenance costs.
This page provides a practical comparison of common engineering metals and alloys, showing their relative resistance to corrosion in different environments such as fresh water, sea water, steam and air. It is intended as a quick reference guide for engineers, designers and students.
This page only relates to materials used for general
mechanical engineering.
Other pages identifying Corrosion /Chemical
Resistance are as follows
In normal mechanical and structural engineering
design materials are selected primarily for their
mechanical properties-corrosion is not an important
criteria. The systems are generally
protected against corrosion by surface
coatings.
Most machines are located indoors and are accessible
for inspection and maintenance. The
exceptions to this are machines used for construction
and agriculture. These machines may well
be used in corrosive environments but they are
generally regularly maintained and some level of
corrosion is acceptable.
In process engineering corrosion is a very important
design factor and materials are selected primarily on
their resistance to chemical attack
(corrosion). Surface coatings are often
not considered because of the risk of contaminating
the process stream.
The table below compares the corrosion resistance of common engineering materials in non-chemical environments such as water, steam and air. Ratings range from 0 (unsuitable) to 6 (excellent) and provide a general guide for material selection.
Ratings 0 = Unsuitable, 1 = poor, 2 = Fair, 3 =Fair to Good, 4 good, 5 = good to excellent, 6= excellent.
| Fresh Water |
Sea Water |
Steam |
Steam Cond'te |
Air | |
| Metal | Static/Turb | Static/Turb | Dry | Wet | City/Indust |
|
Grey Cast Iron- Plain or Low Alloy |
4/3 | 4/3 | 4 | 4 | 3 |
|
Ductile Iron (High Strength ) |
4/4 | 4/2 | 4 | 4 | 3 |
|
Cast Iron Ni_Resist. (14% Ni, 7% Cu, 2% Cr bal Fe) |
5/5 | 5/5 | 5 | 5 | 4 |
|
Ductile Iron Ni_Resist. (24 % Ni, bal Fe) |
5/5 | 5/5 | 5 | 5 | 4 |
| Mild Steel- Low Alloy steels | 4/3 | 4/2 | 4 | 4 | 3 |
|
Stainless Steel Ferritic (17% Cro) |
4/6 | 1/4 | 6 | 5 | 3 |
|
Stainless Steel Austenitic (18% Cro ,8% Ni ) |
6/6 | 2/5 | 6 | 5 | 4 |
|
Stainless Steel Austenitic (18% Cro 12% Ni, 2.5% Mo ) |
6/6 | 3/5 | 6 | 6 | 6 |
|
Stainless Steel Austenitic (20% Cro 29% Ni, 2.5% Mo,3.5% Cu ) |
6/6 | 4/6 | 6 | 6 | 6 |
|
Hastelloy Alloy (55% Ni, 17% Mo,16% Cr, 6% Fe, 4% W) |
6/6 | 6/6 | 6 | 6 | 6 |
|
Inconel (78% ni,15% Cr, 7% Fe) |
6/6 | 4/6 | 6 | 6 | 6 |
|
Copper Nickel alloys (Up to 30% Ni) |
6/6 | 6/6 | 5 | 6 | 5 |
|
Monel 400 (66% Ni, 30% Cu, 4% Si) |
6/6 | 6/6 | 6 | 6 | 5 |
|
Nickel Commercial (99% Ni) |
3/5 | 6/6 | 6 | 6 | 4 |
| Copper and Silicon Bronze | 6/5 | 4/1 | 5 | 6 | 5 |
| Aluminium Brass | 6/6 | 4/5 | 5 | 6 | 5 |
|
Bronze (88% Cu,5% Sn,5% Ni,2% Zn) |
6/6 | 5/5 | 5 | 6 | 5 |
| Aluminium Alloys | 4/5 | 0-5/4 | 2 | 5 | 5 |
| Lead (Chemical or antimonial) | 6/5 | 5/3 | 0 | 2 | 5 |
| Silver | 6/6 | 5/5 | 5 | 6 | 6 |
| Titanium | 6/6 | 6/6 | 5 | 6 | 6 |
| Zirconium | 6/6 | 6/6 | 5 | 6 | 6 |
A corrosion resistant material is one that can withstand chemical or environmental attack without significant degradation.
Materials such as titanium, zirconium and high-alloy nickel materials offer excellent corrosion resistance in many environments.
Yes, but its performance depends on the grade and environment. Some stainless steels are susceptible to chloride attack.
It prevents failure, reduces maintenance costs and ensures long-term reliability of engineering systems.
Coatings can provide protection, but in critical applications materials are often selected for inherent corrosion resistance.