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Chrome Plating Problems on Gravure Printing Cylinders/Rolls
Current question:February 21, 2021
It is now 7 yrs at our company that we face lines on the printed areas what is it that causes this lines we polish the cylinders and also we filter INKS but they still appear most especially on white surfaces lines poo f cyan and blue mostly. Please help me on this to solve the issue.Bonface Lagat
- Nairobi Nairobi Kenya
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Q. Chrome peeling problem: We gravure print using chrome plated cylinders. The cylinders consist of a steel base which is copper plated then engraved for the print image. A copper plating is then applied over top to extend the life of the cylinder in the press. In gravure the cylinder is partly immersed in ink. The cells of the engraving fill with ink. As the cylinder turns the excess ink is wiped from the non-image area by a metal blade. The cells transfer the ink to the paper as they contact at a nip and the process begins again.
We have been experiencing a chrome peeling problem with our cylinders. The problem has been most prevalent with one of three suppliers, but all three have had peeling to some degree. The chrome "bubbles up" and peels off in select non-image areas of the cylinder. This never happens the first time they are used in the press. Usually it happens the second or third time we use them to print. We talked with the cylinder supplier who insists that their product is up to spec. They suggested we talk to our ink supplier. We use water-based inks (pH 8.5 - 9). We have talked to other manufacturers who use these inks in similar processes without problem.
The press we print with is a little unique in that it uses inferred drying units (positioned approx. 1 ft from the cylinders in the press).They cylinders are stored on metal racks, uncovered in our warehouse in between use.
I have provided as much details as possible in hopes that someone may have an insight into the cause of this problem. It would be much appreciated.
- York, Pennsylvania, USA
The peeling and blistering problem is most probably in the preparation of the copper before chrome plating. Even though it is well known that chrome is not impervious due to its micro cracking, the copper beneath it is very corrosion resistant to all kinds of commercial inks. This means that even if the ink could penetrate through the chrome cracks and reach the copper, it will not be attacked. Another possibility is an excessive thickness of chrome (more than 1-2 mils which I don't think is your case). Then the problem becomes of mechanical nature (internal stresses and their distribution through the chrome layer). Finally, have you checked the blade pressure with the machine manufacturer?
Good luck,Guillermo Marrufo
Monterrey, NL, Mexico
A. Hello Bill,
I suggest you to check following items:
Cracks going across the chrome layer due to
* thin layer thickness
* too high surface pressure
* weak plating quality
(consequence: corrosion under the chrome layer and the effect is visible as bubbles)
Insufficient adhesion of copper on the base material.
(consequence: chrome bubbles off and peels off because the chrome pulls the copper off due to internal stress).
Possible causes: too much brightener, insufficient pretreatment, etc.)
I wish you a successful trouble shooting.Michael Hekli
A. About 20 years ago I was asked to look at a chromium plated printing plate used by a well known UK printing company. Their problem was very similar to what I think is being described here, but they only had the problem with one type of green ink. I do not recall if it was water-based or not, but I do recall the pH for the ink was quite low. Examination of the failure showed it to be localised in the engraving and was similar to what would be expected by erosion corrosion caused by micro-particles in the ink. That is, where the ink, that has been squeezed into the engraving, comes into contact with the edge of the engraving, the chromium showed signs of erosion corrosion. This in turn then allowed the low pH ink to start interlamellar corrosion to occur, resulting in de-lamination of the overcoats at the interface of the over layers. I hope this may offer an insight into what is going on.
R&D practical scientist
Chesham, Bucks, UK
A. This corrosion of Gravure cylinders isn't uncommon. The problem usually occurs after the cylinder has been run on a press, and then stored before the next print run. After around 4~500,000 meters of printing, the Cr deposit thickness will be reduced by around 30~40%. If the copper preparation isn't thorough enough, or the Cr deposit isn't as thick as you think it is, then corrosion can occur in pits or adhesion can suffer.
In UK around three or four years ago, we had a lot of this problem. One main reason was that, printers changed from organic solvent based inks to water based. With the organic based inks the printer didn't have to be so careful about cylinder cleaning before storage. With the water based inks, cleaning is much more important.
We spent a long time working with customers and printers to improve there housekeeping and production methods. Another problem was Cr thickness. The customers thought that they were plating 10~12 microns, but in fact were only plating 8. After the cylinders had been polished they where down to 6 microns, and by the time the cylinders had been run on a press and put into storage, there was only 3~4 microns left at most. When the printers tried to run the cylinders a second time, the Cr would flake off the copper surface.
The surface area of an engraved cylinder is in reality much larger than the sum of its dimensions would suggest. So customers have to allow some extra time to deposit the thickness they think they are.
We also looked at cylinder storage at printers. New, and used cylinders must be kept dry and clean at all times. After printing they must clean and dry the cylinder thoroughly, then wrap and store the cylinder properly.
If these points are looked at, then you will be able to cure this problem.
Hope this helps.
- Hong Kong
A. Regarding the chrome peeling:
Is the chrome peeled off from the copper or do you see after the print the steel base (or the nickel deposit?)
Where does the chrome peels off, is it on the radius in majority? If yes, the use shields in order to avoid excessive build ups and ask your printers (if they are already not doing it to cut the blade ends approx. in a 45 degrees angle and 50mm wide, if the blade oscillation is on and running about 10-15mm across the cylinder then the blade has a relaxation area.
Do you use filters in your ink, any metal particles in?
Any difference by using different inks on different units?
5-7 micron is enough to print around 1.5 - 2.2 million cylinder revolutions. Please consider that above these thicknesses you may cause a build on cell rim between the wall, that also could led to a "rip-off" during the print, especially if the angle and blade pressure as well as the impression roller pressure is too high. As low as possible from everything, as you longer you enjoy your print run.
- Melbourne, VIC, Australia
I'm looking for a method to buff newly engraved rolls2004
Q. We run coating equipment in the converting business. These are gravure coaters that have coating heads that consist of three rolls, one of which is an engraved cylinder. On many occasions when we place a new engraved cylinder into the machine we often spend many hours of down time because the cylinder is not buffed correctly. This often causes bleed by of the coating between the cylinder and the doctor blade. Our cure for the problem to this point has been to run the doctor blade against the cylinder wet and let it run until the bleed by problem is relieved.
My questions: Is there a quicker method of buffing the roll, once it's in the machine?
Is there a material that could be used for buffing or de-burring of the cylinder, that won't harm the engraving or the chrome finish?Dick Hovasse
- Winchester, Massachusetts, USA
A. Ask the supplier of the engraving and/or chrome plating to slightly polish the surface of the roll before plating it.Guillermo Marrufo
Monterrey, NL, Mexico
Need to increase chrome hardness on plate gravure printing cylinders2004
Q. We are using a horizontal plating system to plate gravure printing cylinders with chrome. Our required hardness is > 900 HV, but we cannot get above 750 HV. We are plating at a temperature of 60(±)1 °C, rectifier current of 9.5 V and 30-40 A/dm2.
Our solution concentration is
Chromic Acid - 280 g/l
Sulphuric Acid - 2.8 g/l
CrO (3+) - 5
Anode-cathode ratio ( approx. 1:1)
Are there any additives we can add to increase the hardness of our chrome. What else can we do to improve the hardness? Any suggestions would be HIGHLY appreciated as this is a very serious problem for us.
Thanking you,Azizur Ch
Electroplating (Gravure Cylinder) - Dhaka, DAC, Bangladesh
Regarding you high voltage maybe the contact's from the rectifier is oxidized. It's normally to use 3,5-4,5 voltage for 30 A/dm2. Also make a analyze for the trivalent chrome, iron and copper. Both these metal's can show a bad resultant by the hardness. I believe all this parameters is your's problems. Normally a chrome solutions have a hardness from 900-1100 HV depending which chrome solution who used.
4th Generation Surface Engineering
Consultant - Arvika, Sweden
A. Dear Azizur,
I think you need to correct your basics. Lower the temp to about 55-57 °C and increase anode-cathode ratio to 2:1. Also check for metallic contamination as they bring down the hardness(IRON,COPPER etc. ALL COMBINED NOT MORE THAN 15 gm/lt). Try high speed non etch baths from chem. providers say HEEF-25 they do have better hardness, throw and corrosion resistance.
ALL THE BEST.
Irusha India - Chandigarh, India
A. Due to the micro crack structure of the hard chrome and the fact that the solvents used in cleaning cylinders after printing attract moisture, oxidation of the copper takes place under the chrome layer.you will see this by looking at the colour of the exposed copper. I have found that a thin wipe of light oil and to wrap the cylinder in plastic solves the problem.Shaun Grenfell
printing - Durban, South Africa
How to check chrome hardness2003
Q. Is there a way to check chrome hardness on a gravure cylinder with a coating thickness of approx. 3 tenths of chrome plated over 15 thousandths of copper?Jack Manifold
graphics - Toronto, Ontario
What causes the chrome to corrode?2004
Q. I am the superintendent of printing operations for a large manufacturer of paperboard packaging in the fast food industry. Our printing operation uses rotogravure technology. The gravure printing cylinder is a steel base plated with nickel, copper and finally chrome. In operation the cylinder is bathed in printing ink and wiped clean with a carbon steel doctor blade. To clarify, two unlike metals, carbon steel and chrome, are in constant contact with an alkali solution between them. Under certain common conditions the chrome plating is susceptible to corrosion. These conditions include the use of blue ink which contain higher concentrations of metals than other colors. Additionally the use of ammonia to maintain printing ink Ph at levels between 8.0 - 9.5 is considered to be a contributing factor.
Can you help me understand what is causing the corrosion condition? I have not been able to narrow down what exactly is causing it. The gravure industry faces stiff competition from the flexographic industry and struggles to maintain environmental compliance. This corrosion problem is yet another nail in the industry coffin. Help me keep the gravure association alive.Kevin Moody
- Stockton , California, USA
A. Chrome is not very resistant to corrosion, certain types of inks will attack it, but it is very hard. That's why you use it on top of your engraved rolls. Copper in turn is soft, very corrosion resistant and much more noble (galvanic potential against chrome). I think your best chances would be to find more friendly grades of inks. Also, there are special chrome baths prepared to increase the corrosion resistance. One is called microcracked or porous chrome and the other is called thin-dense chrome. It may be worth investigating their suitability for your situation.Guillermo Marrufo
Monterrey, NL, Mexico
Chromium plating is rough2004
Q. In electronic copper plating we are getting hardness of 220 hv. Copper Sulphate is at 240 g/l and sulphuric at 65 g/l. But upon hard chrome plating on it we get roughness on the cylinder. Is it because of high sulphuric in the copper bath effecting the hard chrome or some problem in the chrome bath? Do we have to increase the bath concentration for chrome plating of hard coppered cylinders?Dhritiman M [last name deleted for privacy by Editor]
rotogravure - Mumbai, Maharashtra, India
A. What is the hard chrome bath you are using? If you are using HENE process, then try increasing sulphate content in hard chrome bath to ratio 100:1. If you are getting roughness in copper bath, then give activated carbon treatment to the copper bath.N.K.Praveen Kumar
- Secunderabad, ANDHRA PRADESH, iNDIA
Q. We produce cylinder for rotogravure
I prepared new electrolyte but cylinder's surface is stained and milky.
265 g/l CrO3
2,7 g/l H2SO4
Anode: platinised titanium and two lead-tin alloy rods
Cathode: copper plated cylinder
267 ml hull-cell test:
chrome deposition approximately half the plate surface
no rainbow coloured zone
especially low current density zone slightly mat
there is two phase on chrome plated plate
from 0 cm to 2 cm zone is bright
and the other zone is slightly mat
What is the problem?
Can you help me, please?
- Izmir, Turkey
A. To start with, a platinised titanium anode promotes the formation of trivalent chrome as it works to plate. Therefore you are going to have to dummy or porous pot treat the solution or it will shut down from excessive trivalent. A little is OK and some say it is mandatory, but a lot is bad to very bad. I will guess that this is a conforming anode--true or false? I will guess that the two tin lead rods are the anode leads-true or false? If so, they will have to be massive to carry the required amperage. Lead is a lousy conductor.
- Navarre, Florida
? Dear Fikret MUTLU,
motorcycle accessories mfgr.
- Aurangabad, Maharashtra, India
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