Chrome roller plating

[Kaoticor]

Dear Printplaneters

I was wondering if any of you have ever seen the chrome plating come off of a dampening system roller? If so, do you know what caused it?

Thanks for any time taken to post!

 

[Cornishpastythighs]

I have seen 'bubbling' of the chrome that was caused by poor quality chrome plating, I think that the core was not properly treated prior to the plating operation.

 

[Dan Roll]

Several major press manufacturers have, in the past, experimented with skipping some of the steps in proper chrome plating of steel. The process requires first copper plating, then nickel plating, followed by chrome plating. When clever people try to skip the first two steps to save money you end up with a roller that will exhibit pitting of the steel under the chrome. This leads to what looks like bubbles in the chrome if rust forms in the pits or indentations in the chrome if rust does not form. Having the roller properly re-plated should solve the problem. These problems, repeatedly experienced by several large European press manufacturers with chrome rollers over the years are what I believe caused their interest in ceramic rollers (I much prefer chrome rollers for dampening systems over ceramic rollers).

 

[Green Printer]

The press manufacturers mentioned by Dan Roll would blame chemistry manufacturers for the corrosion of the chrome rollers. When the problem was found to be the plating process the press manufacturers offered no apologies or compensation for the lab test and legal fees of the chemistry companies. One of these press manufacturers just recently entered into receivership.

 

[Dan Roll]

The press manufacturers mentioned by Dan Roll would blame chemistry manufacturers for the corrosion of the chrome rollers. When the problem was found to be the plating process the press manufacturers offered no apologies or compensation for the lab test and legal fees of the chemistry companies. One of these press manufacturers just recently entered into receivership.

This is true, but let us be careful to not name names here. There was a lawsuit filed in Europe by a group of press manufacturers against several major European fountain solution manufacturers attempting to hold them responsible for the chrome roller issues. I would love to get a transcript of the proceedings.

 

[Servicetech]

Yes, all it takes is one tiny pinhole and the fountain solution begins getting under the chrome and attacks the roller underneath. it will cause a bubble it the chrome that will eventually flake off.

In the past I found a common issue was on a 40" Komori, when taking out and installing water form rollers it is very easy to ding the chrome vibrator roller with the gear on the form. Some of the older ones were real bad, the rollers were quite heavy, and had a steel gear on one end, brass gear on the other.

A small ding may not seem like much, but it will eventually become a problem. I always wrap the chrome roller in cover stock to protect the surface while dealing with the heavy 40" water form.

The same damage on a chrome pan roller will cause the this problem much faster, as the roller is partially submerged in fountain solution. The pan roller also requires a top shelf plating, for the same reason.

On a side note, I was in a plant several years ago that was experimenting with a polished stainless steel pan roller on one of their presses, It was running fine. I have not been there since so i don't know what the final outcome was.

 

[Dan Roll]

Corrosion of the steel surface below the chrome plating is caused by electrolysis. As long as the fountain solution has sufficient conductivity (pH is largely irrelevant to this process) the flow of fountain solution (an electrolyte) around or across the roller surface creates a galvanic battery which will erode the least noble metal available to it. As long as the chrome surface has copper and nickel under it, there is little, if any, potential for corrosion to the steel underneath. A layer of just chrome on steel is porous enough that electrolysis will take place right through the chrome, although this does not usually happen quickly. To accelerate the process all you need is a little current (it does not take more than a few milliamperes) in the roller or solution. A visit to a plating company is often an eye-opener for printers to see how rapidly metal can be applied to or removed from a surface and how little electricity is needed.

 

[safepackltd]

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