Chrome plated hydraulic cylinder rods have pits, pinholes, and peeling problems

A. Since you are new, please try to get the vendor to visit and help you troubleshoot, Richard. Hard chrome plating is difficult to start up without experienced help, and may mean a lot of lost time and unnecessary waste. My suspicion would be that the problem is mechanical prep rather than the plating itself -- but it can be a long road if you go by guesses :-)

Good luck.

A. The highest probability is that you have microscopic burrs on the shaft from a machine operation or a blasting step. I doubt if the HEEF 25 is at fault, unless you have a very particulate-contaminated tank. Do not stir up the sludge on the bottom of the tank unless you have several hours to let it settle out.

A. When there is problem do not panic; of course there is a problem, but a solution also.
Your problem is roughness.
What is solution? Filter the solution.
Check your anode quality from a reputed lab.
It should be 90% lead and 10% tin
Then comes your solution part.
Analyse for chromic acid, sulphate, iron, copper, zinc.
Chromic acid to sulphate ratio should be properly maintained as per supplier data sheet.
Temperature, C.D, as per supplier data sheet.
Precleaning as recommended.
Normally: soak cleaning hot, anodic cleaning, W.R, W.R, acid dip, W.R, W.R, etching, hard chrome, drag out, drag out, W.R, hot water + chrome neutralizer, dry.

A. A long time ago, I used HEEF 25 for plating parts much like yours. I used a lead/tin/silver mesh conforming anode with about a 1 inch spacing. We used about 4-5 amps per sq inch and had vigorous outgassing that cleaned gas bubbles off of the part. We also plated vertically. How do you do it. If those white spots in your picture are your pits, those are massive pits and not pinholes.

A. I am an experienced hard chrome plater for the last 30 years. I specialised in Hard chrome plating of piston rods, engine valves, strut rods, pneumatic cylinders, etc. Your problem of pin holes can be solved by giving a light wash in 1:3 HCl and then polishing with fine grade sheet, and etching at low amps at the same temp of 60 degrees and start the rectifier by increasing the amps slowly step by step (not sudden downing the etch switch) and stop the bath after one hour and rotate the rod so that the sides facing the anodes will go down and the sides facing up and down will face now the anodes. Reverse etch for a few seconds. Then start the rectifier very very slowly to avoid peel off to the required amperage.

I have faced such problems in pneumatic pistons of earth moving equipments and new piston rods of plastic machines, and we solved all pitting by rotating every hour.
Cheers
Rajaraam

A. Dear Richard Pho,
The problem is probably caused due to hydrogen embrittlement as you have suggested that these rods are Induction hardened and ground. I feel after stripping chrome and prior to grinding, stress relive these jobs @ 180 °C for 1-3 Hours and then grind. After grinding, if you can, super finish these components and follow standard pre treatment procedure for hard chrome.
Best luck

A. It sounds like you may not be allowing the solid rods enough time to heat to the bath temperature whereas the hollow rods will obviously heat more quickly.

A. Hi John,

At a guess the plating is probably chrome plating. It looks like corrosion under the plating has caused lifting of the coating. This happens when either there is an inadequate undercoat of nickel or copper or when there is no undercoat the chrome plating is too thin (less than 0.002"), although even relatively thick chrome plating is no guarantee against corrosion as it is micro-cracked and if you are unlucky a route to the base metal will still be present.

A. From the photograph the piston rod is working in a marine environment where corrosion can take place very rapidly, more so if the piston rod is heat treated. Please ensure that underneath Electro less Ni with phosphor content of 8-12% is deposited around 20-25 microns and 100 micron of Chrome plating. The pitting problem will be solved. Good luck

A. Hi,
This is very bad chrome; it's not pinholes, it's chrome plate over rusted steel. There are areas that have FeO2 in the substrate which is not dissolved in a acid. If it would be pinholes it should be more smaller.
I'd say it's bad pretreatment before chrome. They talk about pinholes, but I have never seen it there and I have worked with chrome.

Pinholes, I think, you can see by microscope but not visual checking.

Regards

A. Good day John.

I have been following this post, and I must agree with Terry's and Ander's postings that there is a problem with the pre-treatment/plating of the substrate before chrome. Given the fact that this is a hydraulic ram, one would think that the lubricants involved would offer a measure of corrosion protection.
The appearance of blisters on the chrome clearly indicate adhesion issues and insufficient chrome thickness.
My opinion is that the substrate is not properly cleaned/prepped as various steels contain various metallic compositions. The ram obviously is a hardened steel, possibly heat treated, and requires special treatment measures to deal with these facts.
I think that this ram requires a hard chrome process (without a nickel underlay).
Hope this helps.

Regards,

A. Hi, NAKUL,

I am not wrong, this is rotogravure industry. And that's supposed to have a copper process prior to the final hard chrome plating.
For the white spot issue, I assume you have already done hull cell and never detect anything on hard chrome solution. We did encounter the similar issue before, suggest to look into Copper plating process.

Another possibility is copper layer been over-etched in chrome solution, maybe caused by too long idling time in chrome bath before you turn on current.
If this issue only happened on stripped roller, please look into your de-chrome process as well.

Regards
Raymond

A. That does not look like corrosion, it looks like bad adhesion. Suspect your NiCl strike is not activating the stainless steel, that the metal has climbed, go back check the metal content, get it down, Raise the HCl, then try again.

A. Hi. Robert may well be right, but I'm not so sure, based on the numerous tiny spots (which might have been more obvious to me in the original full scale photos that in these reduced & excerpted photos. To me it does looks like corrosion -- but not general environmental corrosion: acid damage ... like someone wiped them with bleach, which may not be unheard of in these Covid-19 days :-(

Were both rods on the same piece of equipment? Do the two problematic rods have anything else in common with each other except being on the same piece of equipment? Were they from a lot of just two or randomly selected for this machine from a larger lot? But I'm just guessing, not claiming expertise in finding cause from photos :-)

Luck & Regards,

A. Hi, Ron.
Please refer to the similar problem of John from December 8, 2015 on this post and following answers of Brian and Mahendra. My impression from your photos and the equipment service conditions (50 degree C and "harsh environment near shore") is that your case is more corrosion problem, than adhesion. Indeed, your shaft is "SS316 with 40-micron hard chrome coating", but 40 micron chrome without nickel or EN underlayer is not enough in high salt environment. I shall recommend to add 40-50 micron of high phosphor EN before chrome plating.
Good luck
Alex

A. Yes, it seems to be peeling.

A. Hello Dante.
a) Some information is missing in your post. Assuming you use a classic Chromic/Sulfuric bath and plate Chrome on Steel substrate - it may be a problem with your electrical set-up.
Your long rod has a large surface area ~1500 sq. inches.
It means at current density of 2-3 ASI you push through your rod ends around 3000-4500 Amp. The ends are only 1.5 inch in diameter, they may be overheating.
b) You did not provide a photo of your "pin holes", so it is difficult to advise something. If there is not enough flow in the tank (agitation or liquid circulation), there is a chance to see "gas pits", as Hydrogen bubble sticking to the part will prevent Chrome to deposit.

Just my 2 cents...

A. Instead of using air agitation I prefer two Eductor pumps operating from two opposite sides of the plating tank for circulation of Plating Solution,