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

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!!

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?

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

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 )

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

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

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

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.

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.

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)

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

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

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)

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

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

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

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

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

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

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

Thank you