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Corrosion of chrome plated parts
Q. We are plating hard Chrome (approx. 20 microns) on mild steel 'front-fork' for two wheeler industry using non-fluoride catalytic chemistry. We are getting a Neutral Salt spray life of about 15 hours. Most of the time it is observed that some individual rust spots are observed after 4-5 hours of neutral salt spray test but the area of the same doesn't increase. This is considered as a failure as per rating no. 10/9.75. Why does this happen and how can we control it? How can we increase the salt spray life to about 60 hours with out giving a nickel undercoat? The raw stock are ground till the roughness of the substrate is 0.08 micron (Ra value). After Cr plating they are again ground to achieve the above roughness. Does the roughness factor have an impact on corrosion? Does the porosity of substrate have an impact on corrosion? What instruments / methods can be used to measure the porosity?
Vijaykumar- India
2002
A. You can try the chrome chemistry with he organic additive which can give more number of cracks per linear centimeter and more the cracks higher the corrosion resistance.
Harish Gurnan- Ahmedabad, India
July 18, 2009
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