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Trouble-Free, Economical Electroless Nickel Plating


By Jim Wetherald, Ronatec C2C

How to properly set up a mid-size, RoHS-compliant EN line without breaking the bank.

Over the last 35 years, Ronatec has supplied electroless nickel (EN) to the automotive, aerospace, electronic, food, aquatic, plumbing, decorative, and naval industries. Our team has identified that many of the technical “problems” we are asked to resolve that relate to user error and equipment in use. While there is the occasional chemistry issue, most can be easily avoided by initiating some simple and inexpensive actions during the line design phase and chemical selection process. This article is intended to illustrate the most cost-effective ways to “set up” a line, while at the same time maintaining the highest level of quality and keeping it simple.

For the purposes of this article, we will be setting up a line using a standard mid-phos, RoHS-compliant, bright electroless nickel line. The line is designed to plate aluminum. (Minor variations may apply if the goal is to plate a different substrate than the above, i.e., copper, magnesium, or steel).

Tank Construction. Various types of tanks are needed on an EN line. Please contact us for schematics of tanks designed that are prefered in the industry.

Tank Material. The Ronatec team prefers polypropylene tanks for a few reasons (most cost effective, last the longest, easy to repair, light weight, etc.). All polypropylene should be ½ '' thick material, with the exception of the tank floor, which should be 1'' to avoid cracking if parts drop. Electroless nickel tanks should be made of natural poly pro. If steel is preferred, or if steel is only available, please contact Ronatec for some helpful tips to avoid “plate-out.”

Insulation. All hot tanks should be insulated, with at least a 3-inch separation between the inner and outer walls. Insulation allows a tank to achieve desired temperature faster as well as stay at the desired temperature with the use of less energy. (Note: Use a high-density foam.)

Lids. Using tank lids on hot tanks is a great way to save energy. Lids also keep unwanted “alien” materials out of baths. They are inexpensive and always help.

Girths. Larger tanks may require girths. Make sure all girths are incapsulated to avoid corrosion under insulation. Contact us for tank size to girth ratio charts.

Welding. All meeting points/seams should be triple welded for obvious strength reasons, and shaved to avoid “plate-out” contention areas.

Tank Floor. All tank floors should be flat, with the exception of the electroless nickel tank, which should be a “cone bottom.” This helps eliminate plate-out and extends time between tank passivation. Contact us about cone bottoms on flat surfaces.

Legs. Taller lines may require legs for tanks to reach the desired height. Legs should be built into the side walls of the tank and supported by feet. Use a cross beam on larger tanks to avoid sagging.

Overflow. All rinse tanks should have a cascade overflow, when possible. It saves money and provides superior tank cleanliness.

Heat Exchanger. If the facility has boiler capabilities, then an external heat exchanger is by far preferred for a number of reasons (energy savings, limited bath exposure, exchanger life, etc.). There are also external electric heat exchanger options. The main idea is to heat the electroless nickel without plating the heater. Unless unavoidable, do not use over-the-side heaters or internal heat exchangers. Tanks that are normally heated are highlighted in the following section.

Temperature Controllers. Controllers are best determined by the heat exchanger manufacturer. Ronatec prefers a controller that has both a high and low set point. If funds are available, using a “timer controller” can save on energy costs and avoid plate out in that they can be set to lower when bath is not going to be in use. Wrap controllers in clear plastic to avoid internal corrosion (steam, splash, etc.).

Pump. Electroless nickel pre-treatment (soap, deox, etc.) agitation and turnover ratios should be determined by their specified manufacturer (mostly not required). Make sure to check with the pump manufacturer for requirements based on tank size and material suggested by the chemistry being pumped. On tanks that require a pump, intake should be from the center bottom of the tank for maximum circulation.

Filtration. For the most part, the only tank on an EN line that requires filtration should be the electroless nickel tank. There are typically two types of filtration for electroless nickel tanks: filter bag or filter chamber. For the purpose of this article, Ronatec prefers the filter bag option as it is the most cost effective, is reusable, limits pump pressure, and allows for continual operator inspection. Ronatec prefers to mount the filter bag system on the rear of the electroless nickel tank—off a shelf as to maximize tank surface usage area. Contact Ronatec to see the recommended design.

Plumbing. Ronatec prefers CPVC plumbing. Make sure to use a technician who understands your heat exchanger system, while taking into consideration the chemistry involved.

Ventilation. Electroless nickel should be ventilated. Check with local authorities to make sure ventilation requirements are being met. Most tank manufacturers provide a compatible ventilation/exhaust system.

Electroless Nickel Feeder/Controller. While not required, an electroless nickel feeder can save money in the long run in that it can eliminate human error. At the same time, on many occasions, they can cause problems. The choice comes down to funds available. Contact Ronatec for information regarding the various types of controllers.

Splash Wall. Separate all electronics, plumbing, and sensors from chemicals with a splash wall to prolong equipment life. It is a very inexpensive way to maximize equipment value.

Agitation. Again, refer to the pretreatment chemistry’s manufacturer for agitation requirements. Electroless nickel should always have agitation. For EN tanks, Ronatec prefers “solution agitation” for multiple reasons (added brightness, prevents shadowing, eliminates contaminants, etc.). Use CPVC plumbing along the bottom of the tank to pump filtered solution back into the bath. In this instance, more is better as some parts require more agitation than others.

Tank Placement. Provide plenty of space for tank maintenance (filter alterations, etc.). If possible, limit exposure to the exhausts of other baths as contamination will shorten bath life. (Please contact Ronatec for a schematic of our preferred electroless nickel tank design.

Electroless Nickel Tank Line Order. The ideal electroless nickel line, for the purposes mentioned above, should have 18 tanks (less tanks can be used by “doubling up” on tanks, but this is not recommended. Contact us for additional options). The below assumes a room tempurature of 70° F:

1. Aluminum Soak
2. Rinse
3. Aluminum Etch(Caustic based or Acid based)
4. Rinse
5. Deoxidizer(Chrome Free)
6. DI Rinse
7. Non-Cyanide Zincate
8. Rinse
9. Zincate Strip
10. DI Rinse
11. Non-Cyanide Zincate
12. Rinse
13. DI Rinse
14. Alkaline Electroless Nickel Strike
15. DI Rinse
16. RoHS, Mid Phosphorous, Bright Electroless Nickel Strike
17. Rinse
18. Hot DI Rinse

 

Many have asked why an alkaline electroless nickel strike and a second non-cyanide zincate bath are so vital, and how adding these additional tanks to a line might save money. The answer: Double zincating is now the standard in electroless nickel plating, allowing superior adhesion and eliminating pitting/blistering. You can reuse the initial zincate tank if space is limited, but be sure to avoid cross contamination with zincate strip.

The alakine electroless nickel strike is the most cost-effective bath on the aforementioned EN line. A typical RoHS-compliant bright electroless nickel bath should reach 8-9 turnovers over aluminum, if run properly, without the use of an alakine strike. (Please contact Ronatec for the proper turnover calculation based on your material used). However, by adding the alkine strike, that same RoHS EN bath should reach 10-13 turnovers. That’s a huge increase in bath length. The reason most EN tanks over aluminum only last to 8-9 turns is because of their build up of zincate and conversion of hypophosite to orthophosphite. The strike eliminates zincate build up in the final EN bath. The best part is that alkaline strikes are fairly inexpensive to run, while the RoHS electroless nickel tank is the most expensive on the line. By adding an alakine nickel strike the value of the RoHS electroless nickel tank has doubled.

Pre-Treatment Chemical Choices. Choosing proprietary pretreatment over “home brews” can be a difficult choice. For obvious reasons (disclosure: Ronatec supplies proprietary chemistry), Ronatec prefers proprietary pretreatment chemistries. There are some huge cost advantages to using proprietaries vs. home brew alternatives. These include tech support (priceless), chemistry advantages, and Mil-Spec approvals (required). With that said, initial start-up costs are much less expensive when if one makes their own etch, deoxidizer, and zincates. Please contact Ronatec for a list of home brew formulations, which can also be found in the Metal Finishing Handbook and/or online.

If it is decided to go the proprietary route, choose suppliers wisely:
 

  • Is the supplier’s pricing secure or do they raise it often? (i.e., right after they secure the business)
  • Does the supplier offer quality customer service? (i.e., ease to order, stock material, etc.)
  • Does the supplier offer technical support/expertise or refer to another supplier/manufacturer? THIS IS IMPORTANT! The chemical supplier should, in most cases, be able to provide tech service!

Electroless Nickel Chemical Choices. The most important part of the chemical selection process should be the choice of an electroless nickel supplier. This should include the non-cyanide zincate, alakine electroless nickel strike, and the RoHS-compliant electroless nickel. Work with a direct manufacturer or a stocking distributor. Both have huge advantages and each situation is unique.

A good supplier will:
 

  •  Provide around-the-clock technical support
  •  Back up their chemistry financially
  •  Keep chemistry in stock
  •  Provide free sample analysis
  •  Provide free salt-spray testing
  •  Provide a list of notable electroless nickel platers who they work with

Always remember that less expensive EN is not always the best, while more expensive EN does not always make it better. 
 

  • Check nickel concentrations (g/l) in the A component vs. price. Most EN formulations today use an 8 g/l “A” component formulation.
  • Check proven turn-over levels. Does the EN reach 8-10 turnovers over an aluminum substrate with out the use of a strike? It should. 
  • Does the formulation utilize “1 to 1” (A to C*) replenishment combination or “1 to 2”? Ronatec prefers the “1 to 1” replenishment model, as it:
  1. Costs less to transport (Never pay to ship excess water when possible).
  2. Is easier to use.
  3. Usually costs less when compared to the same replenishment of a “1 to 2,” by volume added.

CONCLUSION

This article is meant to assist with a new line design. If a line is already in place and assistance is required, please feel free to contact Ronatec. We are available to help make some suggestions. This information is based on a collective analysis of our team. We are always looking to expand our knowledge and appreciate you suggestions.

BIO
James Wetherald serves as a technical sales representative for the Electroless Nickel Division of Ronatec, C2C, Inc., based in Carlsbad, Calif. He works closely with direct customers and distributors addressing issues with a “hands-on” approach.

Jim graduated from San Diego State University with degrees in Integrated Financial Systems and Applied Mathematics, and has studied chemical engineering and JIT systems management. His six years in the metal finishing industry, combined with excellent training from Shawn Wetherald, Mike Aleksinas, Joe Zabielski—as well as other well known industry experts—has made him a valuable asset in electroless nickel problem solving and its related applications.


ABOUT RONATEC
Ronatec has been a leader in the electroless nickel industry since the 1980s. Ronatec works with facilities across the United States, Mexico, Canada, China, Brazil, Thailand, and Ireland. Ronatec operates warehousing facilities in eight convenient locations, providing shipping and analysis on a same-day basis.
 

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Aerospace  •  Automotive  •  Decorative  •  Electronics

 

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