Shining Up Bright Nickel Plating Baths

Article From: Products Finishing, , from Products Finishing

Posted on: 12/1/2002

The chemistry in a bright-nickel-plating bath is not inexpensive. Waste treatment of nickel-plating wastes can be expensive. Meridian found a solution that not only lowered costs, but improved efficiency...

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Washer cleans bumpers

Washer cleans bumpers after the buffing process. Bumpers are then staged in an overhead area prior to plating.

six load/unload stations

There are six load/unload stations where bumpers are inspected prior to plating.

Adsorption system filters

Adsorption system filters the four bright-nickel-plating tanks to remove impurities. The system has helped Meridian cut filter changes dramatically.

Meridian Automotive Systems (Ionia, MI) plates a lot of bright nickel, which, of course could be related to the fact that it plates 6,000-6,500 truck bumpers every day through a duplex nickel system. These bumpers are plated in four, 10,000-gal bright nickel tanks on two automated lines. Because the amount of nickel used in the company's operation is tremendous, it wanted to find a way to keep as much of it in the bath as possible, and at the same time improve profitability, increase efficiency and lower waste disposal costs.

Bill Slater, plating manager, and Joe Flanders, plating laboratory manager, decided to focus on the bright nickel plating tanks. Bright nickel-plating chemistry is not inexpensive, and the filtration used to maintain the bath can be messy and time consuming. "We used to have 208 filter changes a year when we did carbon treating every four months. Now we have only 64 and no batch treating. That is a filter change every 45 days, compared to every two weeks with the previous filter system," noted Mr. Slater. "Our biggest concern, however, was passing the OEM ductility specification for bright nickel of 11%." (ASTM B490).

The filtration system Meridian installed uses an adsorber polymer to purify the bright-nickel-plating baths. The one system is plumbed to each of the four plating tanks. The adsorber polymer unit is used on one tank each day for 9 ½ hours. "Originally, we thought we could only use one filtration system per tank," stated Mr. Flanders "And, at first, we kept it on one tank until we noticed that it was removing a small portion of the carrier additive. That is when we started using a four-day cycle, running a different bath through the system each day. We could do two baths in one day if we needed to."

Since using the system, Meridian has not had to do any batch carbon treatment. Because of this, they do not need permanganate or peroxide treatments. "Once a year we run five gal of 10% isopropyl alcohol through the system to clean the resin," stated Mr. Flanders.

The adsorber polymer continuously diverts part of the bright-nickel-plating bath to treatment; production is never interrupted. Production is five days a week, two shifts a day and some Saturdays.

The plating thickness specifications on the bumpers are 33m total nickel. Bright nickel makes up about 8m of that. During the first year of operation, Meridian plated 2,000,000 bumpers. Current use was 42,000 amp/hr. From this you can extrapolate to 5,469 amp/gal/year. Cathode efficiency was 96%, suggesting that about 481,000 lb of bright nickel were plated with no batch carbon treatment.

In batch carbon treatment, the methodology is to take out the wetting agent first, the brightener second and the breakdown products and carrier brightener third. The order with the adsorber polymer system is to take out the breakdown products first, carrier brightener second.

Unfortunately, the system is not 100% closed. After every regeneration cycle, the adsorber polymer must be rinsed. Despite its best efforts to minimize solution loss, 10-11 gallons of nickel-containing solution is lost. This equals about 42 gpd from the tanks; however, Meridian sees this as reasonable, considering the number of bumpers it processes each day. More solution was lost during treatments and filter changes with the old system.

To measure the effectiveness of the adsorber system, Meridian measures total organic carbon (TOC). Fresh bright nickel baths run from about 7,500 ppm of TOC. Once the bath reaches about 20 g/liter TOC, deposit properties deteriorate. The adsorber polymer functions well in the 10,000-12,000 ppm TOC range. TOC levels below that tend to cause higher additive losses and more hours of operation for the polymer system without any improvement in deposit properties.

As is show in Figure 1, Meridian's TOC levels have been held between 10,000 and 12,500 ppm. The deposit ductility has remained constant at 11% or greater. No F006 waste has been generated from batch carbon treatment, because there is none. Solution from the regeneration of the adsorber polymer is treated in the company's waste treatment system for the nickel-plating lines.

The adsorber system has helped the company save money, improve efficiency and lower costs. Meridian estimates that the total annual labor and material cost of batch carbon treatment was about $2,600 per tank and another $5,200 for filter changes. The cost of replacing the solution was estimated at $21,600 per year. The cost for filter changes now is about $83 for each change, not counting any components that may be needed. Since the system's filter is only changed 64 times per year, the cost is $5,312 per year for all the bright-nickel-plating tanks. Also, Meridian sends 13,760 lb less sludge to landfill annually.

Considering the size of the two bumper plating lines, this is significant, since bumper plating can generate a lot of hazardous sludge due to dragout. The lines at Meridian were specially designed for efficiency, making use of overhead space, but at the same time allowing sufficient area to work in and around the systems. Meridian stamps the bumpers from steel and sends them to the plating shop. First, they are inspected, buffed and cleaned, and treated with a rust inhibitor. After drying, the bumpers are stored on one of two storage bays; however, no bumper stays in storage long (three days maximum). When they are called down for plating, they are again inspected at one of six racking stations and then racked for plating. The number of bumpers on a rack depends on whether it is a front or rear bumper and the size. Once racked, parts go through a soak cleaner, power spray, anodic cleaner, cathodic cleaner, spray rinse, activating acid, another spray rinse and then the nickel strikes prior to the actual plating (See Fig. 2).

The anodic cleaner is a reverse cleaner. The cathodic cleaner is used to reactivate bumpers that have been stripped and/or repaired by buffing are clean prior to plating. If this cleaning step was not included, the plating would peel from the bumpers. The combination of anodic and cathodic cleaners provides for excellent plating adhesion. All the cleaner chemistry is supplied by ChemProtect.

Both plating lines are controlled with an elaborate computer system supplied by Trimble (formerly Geotronics). Every aspect of the plating line is controlled and viewable via the system, from the buffing area to the plating tanks to the racking/unracking area. Also, all information is recorded and can be viewed as bumpers are plated. If a bumper is in the nickel-plating tank, all process information up until that point can be reviewed, including time in tank, temperatures, amperages, bath concentrations and more. Another important feature is the Dynamic Schedular. It can bath out a tank or cell at anytime, even while the bumpers are in the tank. All information is stored in a database in case it needs to be retrieved later.

The final OK on the plated finish comes from the plating lab where a number of tests are performed. A bumper is routinely pulled from the line and plugs are taken out of it. These plugs are tested for thickness of all the plating layers. Sulfur foils are done to specification, since sulfur levels can change the activity of the nickel. Meridian has three CASS test corrosion chambers for testing bumpers, and it also sends bumpers to Kerry Beach and Montreal for corrosion testing. It also anchors bumpers on its roof in Ionia for weatherability testing. The big automotive companies also have their specifications that must be met and certified. Meridian is able to do this in its testing lab. The company is ISO 14000, ISO 9001 and Q1 certified. The future is bright for Meridian Automotive Systems.

    Min Nom Max Drip
1 0,1 & 2 Soak 330 397 440 5
2 3 Power Spray 60 72 110 0
3 4 Anodic Cleaner 67 77 100 0
4 5 Cathodic Cleaner 60 79 1108 L
5 6 Dip Rinse 10 7 110 0
6 7 Rinse 37 34 110 0
7 8 Acids 130 184 220 0
8 10 Rinse 20 37 40 0
9 17 & 18 Strike 120 122 220 8
10 19-24 Semi-Brights 28 .SB nom TIME 2116 28 10
11 26 (1 & 2) High Sulfer Strikes 95 120 220 5
12 27 & 28 Brights 44 .BN nom TIME 624 44 5
13 29 (1 & 2) Microporous 50 54 120 6
14 31 Rinse 5 28 40 0
15 32 Rinse 10 43 47 0
16 34 Activation Dip 40 59 80 0
17 35, 36, 37 Chromes 120 .CR nom T_N 150 279 12
18 38 Reclaim 1 6 90 0
19 39 Rinse 1 27 90 0
20 40 Rinse 1 69 90 0
21 41 CFT (Hot Water Rinse) 35 47 90 0
22 42 Hot 35 52 90 0
  Unrack 35 165 220

 

  - Plating Times That Are Used (In Seconds)  
2 Minutes - Load a rack in preplate and send out. 2 Minutes Total
39 Minutes - Rack released from preplate to queue area. 41 Minutes Total
11 Minutes - Queue area to soak tank - beginining of plating. 52 Minutes Total
85 Minutes - From soak tank to unloading station. 137 Minutes Total
0.91 Minute - Unloading time. 137.91 Minutes Total
1.75 Minutes - Inspection time. 139.66 Minutes Total
16.7 Minutes - Travel time on pixie line. 156.36 Minutes Total
0.43 Minute - Apply backside coating and place on green line. 156.79 Minutes Total
0.21 Minute - Wipe off overspray. 157.00 Minutes Total
38.24 Minutes - Time on green line until assembled. 195.24 Minutes Total
Time The Rack Sent Out In Preplate Until It Reaches Assembly. 3.254 Hours
Fig. 2- Plating process at Meridian.

 

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