Hard Chrome Plating is Peeling

A. 1- I would go for 0.002-0.003" min. conventional watts nickel w/o brighteners, or an all-sulphate nickel. Sulfamate would be a much better option.

2- Your chrome thickness, though not impossible at all, seems high. Is it due to dimensional restoration? If it is intended for wear life increase only, it may be wise to reconsider a thiner plate with less internal stress. It would tend to wear out instead of peeling.

3- Corrosion problems will arise in most aggressive environments unless the steel substrate is protected, which cannot be done with conventional hard chrome due to the constant presence of micro cracks that sometimes penetrate the whole plate in certain areas.

A. There should be zero sulphate in a Nickel Sulfamate Plating Solution ! If sulphate is there, then the sulfamate has broken down and you also have ammonia [on eBay or Amazon] which causes brittleness.

Does your pump alloy contain lead? Is it "leaded steel"? If so, come back and let us tell you how to get adhesion on leaded steel.

A. Chrome 0.015-0.020" thick is OK for conventional restoration jobs, but in this case you mention excessive abrasion and I assume by very large and hard particles (they have to be to cut through the chrome). You also mention pitting. This suggests that there might be chlorides present (you know they are the chrome nemesis). A nickel underplate might help but I think that this application is getting beyond chrome's limit. Maybe you should review other restoration techniques like HVOF or plasma spraying. These processes are capable of such thicknesses and more very easily. They can also be tailored to resist extreme corrosion and abrasion.

A. Pull-off has little to do with thickness.
Bond strength, which depends on substrate material and preparation procedure, as well as internal stress, which depends on chemistry and plating parameters are the important variables.
Hard chrome is always stressed in tension and has less than 1% ductility. So, thick layers always exhibit cracks. If care is not taken to avoid crack penetration through the plate, underneath corrosion of the substrate will destroy adhesion.

? Hi, cousin Dattatraya. Please tell us the details of your own situation, i.e., what is the substrate material (steel, C.I., stainless, copper), the general type of component (rotogravure cylinder, mold, etc.), the solution you are using (Sergeant, HEEF, self-regulating), and something about the issues you are experiencing rather than casting the question in the abstract. Thanks!

Regards,

Hi Melda. At first glance this appears to be a plating problem of the plating not adhering to the substrate, and it is generally the platers responsibility to prepare the substrate so that the plating will adhere. But is this a brand new part or has it been in service? -- because if it was in service, is it possible that the substrate is too soft and was moving underneath the plating.

Some facts you'll need to assemble as a first step include:
1 what is the substrate supposed to be, and is it in compliance?
2 what is the specification for the plating, and is it in compliance?

Then you'll face the tougher work of analyzing a lot of different things ranging from the design of the component to a detailed evaluation of the adhesion force. Many different evaluations are possible, but it has to start with whether the components are in compliance with the existing specification. If you can get back to us with what the substrate is, and the plating specification, we hopefully can help further. Good luck.

Regards,