Letter 21051

Zinc Aluminum (85/15%) Metallising  

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At present Oil Industry is using Zinc metallising for LPG cylinders ( MS material) before applying liquid primer and finish coat. Due to improper handling practices, Zinc metallised layer of cylinder Foot-ring peels off and subsequently starts corroding. As a result, very frequently we have to replace the same. Can we think of Zn/Al (85/15%)metallising due to its better bonding properties instead of Zn(99%) for the Footring portion of cylinder alone and if yes than what would be the commercial implications.

Regards,

SANDEEP JAIKISHEN
LPG Equipment Research Centre (A joint venture of IOCL, HPCL & BPCL) - BANGALORE, KARNATAKA, INDIA

Dear Questioner,

The problem of corrosion on the bottom ring of the LPG cylinders can be tackled by way of

a) Providing a coating of thermoplatic paint providing somewhat better bonding between the MS sheet of the ring material which survives and also remains wear proof. There exist special polymers( Patented Product in US)which can be applied as paint at room temperature and after that - an aluminum skin can be pasted on M S Sheet. Thus msling the bottom corrosion proof . Even then the problem of the coating getting cracked- how so ever it corrosion resistance might be - due to rough handling of the cylinders during transportation always stands.

Hence the second solution:

b) As in our kitchen the cylinders are normally placed on the wet flooring- due to typical kitchen use style where the floors are to be washed at least twice every day- and hence the cylinder bottom always rests on a wet flooring - we need to provide a rubber shoe type of arrangement to the cylinder. A device can be designed such that the shoe also acts as weighing scale and it also gives the LPG content information to the user. Hence the dual purpose of the Cylinder shoe will popularize ensure that the consumer themselves attach the shoe to the barefoot cylinder at their end. Hence the bad handling during transportation also will not affect the corrosion sensitivity of the bottom.

DR H. S. Goyal
- Allahabad, UP India

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