Case Study: Stripping and Replating ENP on 42” Valve Balls

The Situation

Several 42” valve balls in critical service in Europe required refurbishment after extended use in a hostile environment. The original Electroless Nickel Plating (ENP) had worn away over time, and the components needed to be stripped and replated to ensure continued performance.

The valve balls were made from 316 stainless steel, a non-ferrous alloy known for its excellent corrosion resistance, making them well suited for harsh service conditions — but also requiring careful handling during the ENP removal process.

The Technical Approach

Stripping ENP: One Process Doesn’t Fit All

Stripping ENP is not a one-size-fits-all process — the method used must depend on the base material.

Stripping ENP from Ferrous Alloys

You might ask: “How can you strip ENP from ferrous alloys if most chemicals that dissolve nickel also aggressively attack the steel beneath?”
That’s a great question — and one we’re often asked.

At CBE+, we use a specially designed alkaline solution formulated to:

1. Dissolve the nickel layer gradually
2. Avoid attacking the ferrous substrate
3. Form a passive protective layer as the substrate becomes exposed, shielding the material from further chemical attack

This controlled process allows us to safely strip ENP coatings from ferrous components — a task that would otherwise risk damaging the part.

Stripping ENP from Stainless Steel (Like 316)

Stainless steels — including 316, Inconel, and Super Duplex — are generally more straightforward to strip. These higher-grade alloys are resistant to limited nitric acid exposure, making nitric-based solutions an effective option for ENP removal.

However, with more and more alloys being described as “stainless,” it’s essential to confirm the exact alloy and composition, as not all grades behave the same. In some cases, they must be treated more like ferrous alloys.

Stripping Other Materials

1. Aluminium: Typically stripped using nitric acid, but exposure must be carefully controlled. Overexposure can dull or etch the surface.
2. Copper and Brass (Yellow Metals): These are difficult to strip — chemicals that attack nickel often attack these materials even more aggressively, making precise control essential (and often uneconomical).
3. Zinc, Chrome & Galvanising: While CBE+ doesn’t offer these coatings, we do have the capability to remove them effectively as part of component refurbishment.
4. Shot Blasting: A mechanical alternative for ENP removal — but only suitable where surface finish and dimensional tolerance are not critical.

The Result

The 316 stainless valve balls were successfully stripped using a controlled nitric acid process, avoiding any damage to the substrate. A new Electroless Nickel coating was then applied to restore corrosion resistance and surface properties, allowing the components to return to service in demanding operational conditions.

By stripping and replating instead of replacing, we helped extend the component lifecycle, reduce waste, and provide a cost-effective solution for the customer — exactly what CBE+ aims to achieve through our integrated surface treatment services.