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Hard chromium plating for large drum

adv.    

Our chromium plating equipments and experiences have been in small parts. Now I need to repair a large drum (dia. 4m, length 8m). Not all parts of the drum require to be Cr plated. The base material is Cast Iron. Before plated, some parts of the base material of the drum requires to be welded. Very difficult to move the drum. Plating must be done on site. We prepared a large solution bath, but impossible to cover all surface of the drum. The bath will be used for all required solutions. I afraid the surface becomes passive before plating because we need time to replace the solutions. Does anyone who has related knowledges and experiences can help me.

Moh Bahri
Manager - Bandung, Jabar, Indonesia
January 3, 2008

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First of two simultaneous responses --

Dear Moh,
one question. Have you already calculated the total current demand? Maybe it will be the crucial point of your order. Saying nothing of such "details" as base metal and so on please consider rectifier and power issues at first. You should "reserve" 20 kA for hit and 12 - 15 kA for process for a long time. Regarding base metal and all problems concerning pre-treatment you should dispose reverse current. It's not easy business. I wish good luck.

Janusz LABEDZ
- Warsaw, Poland
January 4, 2008

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Second of two simultaneous responses --

Maybe not practical for you application but there is a very specialized approach called box plating where a suitable size shaped reservoir is made to suit the selective surface that needs plating and is attached and sealed to it.

Guillermo Marrufo
Monterrey, NL, Mexico
January 5, 2008

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February 15, 2008

when hard chrome plating cast iron you need amps and you cannot reverse the part because you will bring carbon and other bad things to the surface making the part cover in some areas.
you have one shot if you pull the part up and it is dull but covered you do not have enough amps.
one trick is when you blast parts it is harder to cover if you can get buy just polish the part it will be easier to cover just bring the part up slow to avoid blistering.
I hope what know will help you on your problem the joys of cast iron.

Nick Johnson
- Seattle, Washington

Nick, essentially, you are right when we consider reverse current in general, but in that specific case it seems the only way to make a pre-treatment and plating in one bath. Of course, parameters should be deliberately chosen to avoid bad things. Notice, that iron cast plating always brings that kind of risk.

Janusz LABEDZ
- Warsaw, Poland
February 18, 2008

adv.