This paper highlights two case studies of manufacturers that have replaced, or done studies to replace, stainless steel with electroless nickel-plated mild steel.  In both cases, cost savings could be realized while maintaining or improving product quality.  It is the hope of this author that the information included herein will allow or inspire metal finishers and manufacturers to consider such options to save costs, boost competitiveness and increase finishing sales.

Keywords: electroless nickel-plated steel, stainless steel

Corrosion resistant steels have been in existence for well over a thousand years.  One of the earliest examples is the Iron Pillar of Delhi (Fig. 1).  This Hindu monument was constructed around 400 A.D. from an iron-, and interestingly enough, phosphorus alloy.  Its longevity and corrosion resistance are due to the formation of a phosphate film on the surface of the metal.  After 1600 years in the open air, it has barely corroded, and the phosphate film has grown by just 1/20 of a millimeter.

There are many other instances of historic corrosion resistant steels,  but commercial, large production practicality has come only in the last 100 years with the development of the electric arc furnace (EAF), in which most of today’s stainless steels are produced.

Most corrosion resistant, or stainless, steels today owe their stain and corrosion resistance to high levels of chromium and nickel in the alloy.  There are over 150 grades of stainless steel available on the market today. These can be classified into five groups: austenitic, martensitic, ferritic, precipitation-hardened and duplex.  This study only considers the austenitic alloys 303 and 304, and the martensitic alloy 416R. 

Austenitic stainless steels (200 and 300 series) are generally more corrosion resistant than the martensitic stainless alloys, but as a rule, they cannot be hardened by heat treatment.  Martensitic stainless steel alloys (400 series) can be hardened by heat treatment, but usually are not as corrosion resistant as the austenitic alloys.  Composition comparisons are shown in Table 1.

Drawbacks to using stainless steels in manufacturing include price, machinability, and hardenability.   According to www.worldsteelprices.com, during April of 2014, the Global Composite Carbon Steel Price was $713/tonne, where the Global Composite Stainless Steel 304 Price was $2778/tonne.  Stainless steel costs upwards of 3.8 times as much as carbon steel.

In terms of machinability, as a class, stainless steels are generally more difficult to machine than carbon or low-alloy steels because of their higher strength and higher work hardening rates.  They require greater power and lower machine speed, while shortening tool life and sometimes leading to difficulty in obtaining a fine surface finish.  However, it must be noted that wide variations exist in these characteristics among the different types of stainless steels.

Concerning hardenability, as was previously stated, austenitic stainless steels generally cannot be hardened by heat treatment.  Because of these drawbacks, at least two manufacturers have either switched, or considered switching to, electroless nickel (EN)-plated mild steel.  What follows are two case studies related to these manufacturers’ experience.

HWH Corporation is a manufacturer of load leveling systems for recreational vehicles (RVs) and campers, among other things.  They are located in Moscow, Iowa and employ 300-400 people.  The company was founded in 1967 and for the first 17 years of business they designed and manufactured machines and hydraulics for agricultural customers, including John Deere and Caterpillar.  During those early years in the agricultural industry, they also discovered a niche for supplying hydraulic leveling systems to the RV industry (because the RV industry was currently borrowing agricultural equipment to meet their needs).  HWH has since led the RV industry in hydraulic and air leveling technology.  They've introduced countless novel hydraulic slide-out systems to the market and have brought many other hydraulic/air solutions to the RV market, ranging from hydraulic step systems to air suspension systems to saddle-rack systems, as shown in Fig. 2.  Most of the hydraulic shafts were made from 303 and 304 stainless steel, and while performing well, they were very expensive to manufacture.  Further, during the early and mid-2000s, stainless steel prices rose sharply, and correspondingly, the availability decreased dramatically.  HWH began to look for alternatives and electroless nickel was one of them.

After many discussions with management and engineering staff at HWH, it was decided that for the initial testing, 1026 and 1018 steel tubing plated with 0.0015-in. thick high-phosphorus electroless nickel would be evaluated versus the stainless steel.  Parts would also be baked for stress and hydrogen embrittlement relief.   Some of these parts would be put into service right alongside the stainless steel shafts to see if there were any performance differences.   Other parts would be left outside for extended periods to gauge the relative corrosion protection characteristics between the materials.

After months of successful testing, it was decided to replace the stainless with EN-plated 1026 mild steel on one series of the hydraulic load leveling jacks.  A small EN line was installed and, after overcoming the learning curve of becoming platers, limited production began for one year.  During this time, no EN-plated jacks came back from the field for failure.

The decision was then made to install a large line and change all the stainless jacks to EN-plated 1026 and 1018 steel.  This took about a year to order, fabricate and install.

HWH now plates all their hydraulic jack shafts with 0.0015-in. high phosphorus electroless nickel.  They use the bath to about five metal turnovers (MTO).  At this point, they use this older bath to plate other system parts with EN that would not otherwise get plated, providing even more value to their customers.  They coat hundreds of shafts and hundreds of other parts each day.

During the first full year of change from stainless to EN plated steel, the company’s savings were calculated to be over one million dollars.