Testing times for electroless nickel

Edited by the Engineeringtalk editorial team Mar 7, 2005

Anthony Poeton takes issue with the performance claims of nickel solution manufacturers and asks: "Is the current British Standard to blame?"

With a multi-million-pound investment in electroless nickel coating, including a GBP 250,000 second electroless nickel production line recently installed at our Gloucester factory, Poeton has a vested interest in the quality of the proprietary nickel coating solutions offered by the leading chemical manufacturers.

A large portion of the performance data for nickel solutions is based on a British Standard (BS EN ISO1462:1995) that grades the number of rust spots per square inch on the surface of the coating after accelerated exposure during a standard salt spray test.

This has led to typical claims of 1kh corrosion resistance for most nickel coatings.

However, Poeton's experience over several years appears to contradict the claim and we decided to carry out our own research to test the claims.

Using the salt spray testing facilities in our own laboratories we tested nickels from different companies - all of them claiming 1kh corrosion resistance - using specially prepared mild steel panels as the benchmark material.

We were surprised to find that most of them began corroding after only 40-50h.

The results of this research helped us select the best combination of nickel (we now source ours from Atotech) and pretreatment solutions for our own Apticote 400 electroless nickel coating process.

Our extensive experience of the electroless nickel process has also highlighted the importance of premachining the base material and the need to prepare components correctly for the coating process.

We are certain that it is this experience, combined with the quality of the chemical and pre-treatment solutions, that gives Apticote 400 the significant edge over generic nickel coatings that is evident in our own benchmark testing.

We have further corroborated this laboratory testing with slower acting exterior weather testing on our specially built environmental test rigs.

The limited performance of most generic coatings also led to the development of Apticote 460, our advanced nickel composite.

This family of coatings adds the protective power of low friction polymers to the natural hardness and corrosion resistance of the nickel by infusing polymers into the surface of the coating.

The result is a composite coating that provides greater corrosion resistance, improved dry lubrication and better wear resistance.

For particular applications, coating properties can be tailored to provide specific combinations such as extreme hardness (1000Hv) and permanent lubricity, excellent wear and permanent mould release, maximum chemical and wear resistance, etc Apticote 460 has also allowed many of our customers to substantially reduce their material costs by coating low-cost metals to meet high performance specifications.

For example, parts manufactured from low carbon steel and then coated with Apticote 460 can be used to replace more expensive alloy components with no loss of performance.

And costs are further reduced because the parts are machined from more workable and readily available metals.

To further qualify our research we recently conducted a comparative 150h salt spray test on a section of quality mild steel bar.

The length was divided into three sections - uncoated, generic nickel coating and Apticote 460.

The result was serious corrosion of the uncoated material; surface discolouration and some early signs of rust pitting with the generic coating; and a virtually unblemished surface where coated with Apticote 460.

We believe these results and our own years of experience in applying electroless nickel to actual manufactured components, highlight serious deficiencies in the data provided by some chemical companies.

The results should also convince designers to consult experienced surface engineering experts to help them achieve the best results.

To maintain the confidence of the engineering community, the metal finishing industry needs to review its standards.

Doing nothing could mislead engineers and even undermine manufacturing industry's efforts to improve quality, reliability and durability.