1. INTERNSHIP REPORT Study on Ips corrosion
Submitted By
Monica
B.Tech 3rd year,Chemical Engineering
IIT Madras

2. Percentage should not increase!!
Aim of the project
To study the corrosion of IPS coated fastrack watches and ways to improve the corrosion resistance of coating.
There has been complaints from the market that fastrack watches are more prone to corrosion.
The current percentage return of fastrack watches with corrosion issues is 0.12%
Percentage should not increase!!

3. Options that are explored:
Change of raw material
composition of brass
At present we are using lead free brass Cu- 63% Zn- 37%
Can we give any other additional layer of coating before IPS coating which provides protection from corrosion?

4. Literature study
Zirconium nitride(ZrN) coating gives better corrosion resistance, but it is yellow gold like color which cannot be used for IPS coated watch cases.
Zirconium layer may also offer corrosion resistance.
Microstructure:
Smaller the grain size ,higher the corrosion resistance
References:
Surface and Coatings Technology 167 (2003) 188–196
Mechanical and tribological properties of nanocrystalline surface of brass produced by sandblasting and annealing Linchun Wang, D.Y. Li*,Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alta., Canada T6G 2G6

5. Samples that are tested
Samples from vendor
In-house samples
Corroded samples-Market returns
Tests that are carried out…
Chemical Composition (Using X-Ray Fischerscope)
Microstructure-Grain size
Hardness – (Vickers hardness test )

6. Observations Outside samples-Leaded Brass
(Cu-59.3% Zn-39.55% Pb-1.12%)
Hardness-127 Hv
In-house samples-Lead free Brass (Cu-61.36% Zn-38.64)
Hardness-95 Hv
Hardness value varies inversely with grain size
Leaded brass sample has larger grain size when compared to lead free brass

7. Microstructure-Grain size
Lead free brass
Leaded brass
Grain size – 32 microns
Grain size- 4 to 5 micron

8. Annealing Initial stage-Before forming After the final forming stage
Grain size-42 microns
Grain size-34 microns

9. Conclusions
Lead free brass is having larger grain size compared to leaded brass
This implies there is no significant grain growth after annealing. The operating temperature and duration of process does not lead to grain growth.
Annealing is done only for stress relieving after each stage of forming.

10. We have seen that among top 50 corrosion models based on market returns, all are from lead free brass raw material except 4 which are leaded brass.
Leaded brass would give more corrosion resistance compared to lead free brass since it has smaller grain size.
Additional layer of Zirconium may give better corrosion resistance.

11. Experiment Trials Samples for testing:
1)Leaded Brass-Sample from vendor
2)Lead-free Brass-In house sample (Model-1161)
3)Leaded Brass-In house sample(Model-3001)

12. Types of Plating Trials:
Chrome coating-with regular plating specifications.
Specification:
Zirconium coating-An additional layer of Zirconium of 0.1 micron thickness is plated.
Nickel
10-12 micron
Chromium
0.3 micron
IPS
0.5 micron
Nickel
10-12 micron
Chromium
0.3 micron
Zirconium
0.1 micron
IPS
0.5 micron

13. Pictures of samples after plating
Leaded brass 3001
Lead free brass 1161
The Zirconium samples appeared to be in light grey in color

14. Corrosion Tests that are performed:
1)Cyclic Voltaic cell test
2)Perspiration test
3)Salt spray test
4)Porosity test
5)Tumbling test followed by cyclic voltaic test
(As the corrosion starts after the wear and abrasion of top surface coating)

15. Results of Porosity Test
Corrosion is seen on Lead-free
samples where as there are no signs of corrosion on Zirconium coated samples
Lead free brass-In house

16. Perspiration and Salt spray test
Zirconium
sample
Regular IPS sample
The color of zirconium samples became more darker after the test

17. Cyclic voltammetry Regular IPS coated lead free brass
Zirconium coated lead free brass

18. Impedance Regular IPS coated lead free brass
Zirconium coated lead free brass

19. Zirconium Lead free Vs. Leaded brass(Wear tested samples)
Zirconium lead free brass
Zirconium leaded

20. Results
The intensity of corrosion is same in both regular IPS coated samples and zirconium coated samples
But zirconium coated samples show extended period of corrosion compared to regular IPS coated samples.
Lead-free Vs Leaded brass
In regular IPS sample there is no marginal difference but leaded brass is better compared to lead free.
In zirconium coated samples, Leaded is showing better corrosion resistance compared to lead free brass

21. Future study Colour of the samples Research study on Zirconium
Quantitative test

22. Thank you