Dec. 30, 2024
The objective of this paper is to pass along the knowledge gained from some 60 years of providing chemicals, services, and technology to the hard chrome industry.
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Eric Svenson Sr.Our goal is to help the industry because hard chrome is a critical process thats vital to our economy and our national security. Although this is directed towards hard chrome operations, it also applies to all electroplating processes, whether theyre performed in a job or captive shop.
Process control is becoming ever more important to the success of modern plating operations. This is critical in todays industrial environment, where shops that provide the best quality and the greatest consistency receive the highest prices and the largest workloads. In short, they outpace their competitors by a wide margin.
A plating line is an assembly of process baths that includes cleaners, activators, plating solutions, and various rinse tanks. This includes large, automated plating lines and smaller manual systems. However, many hard chrome operations use fewer tanks because the cleaning is often done by hand, and the activation (reversing) is sometimes done directly in the plating bath, a common practice thats not generally recommended.
"An unhealthy plating bath always produces poor-quality deposits, has higher reject rates, and increases production costs."
Its critical to control these baths within their desired concentration range, regardless of the size and type of plating line. This control includes the chemical concentrations and the limit of impurities that should be tolerated. Of these, the plating bath is the most important because its the lifeblood of the operation.
Thats not to say the other baths arent important because they are. Its just that the plating bath has the highest priority. An unhealthy plating bath always produces poor-quality deposits, has higher reject rates, and increases production costs.
Fortunately, the hexavalent chrome bath is fairly tolerable to reasonable levels of impurities; in fact, its one of the most forgiving of all the plating processes. But that doesnt mean that it should be abused. Quite the opposite, the chrome bath operates best when its ingredients and impurities are controlled within fairly narrow limits. The worst mistake a plater can make is waiting until a problem develops before having a bath analysis done.
The hard chrome bath operates with only two primary ingredients, chromic acid, and sulfate. High-efficiency baths include 1-2 additional catalysts, but regardless, the chrome and sulfate levels are the most critical. These two components require frequent analysis and control. Its very common for excess sulfate to unknowingly enter the bath through the water supply and impurities in the chromic acid used. The increased sulfate throws the chrome:sulfate ratio out of kilter, which results in any number of plating problems.
Sulfate is a true catalyst meaning it isnt consumed during electrolysis. Its concentration only increases from drag-in or from bath additions. The sulfate level never decreases; naturally, its only lost through drag-out, a tank leak, or an overflow. This, along with its huge impact on the plating quality, is the reason it must be closely monitored and controlled.
On the other hand, the chromic acid level gradually decreases in relation to the number of ampere-hours plated. The consumption rate for chromic acid is typically around 100 lbs. per 400,000-ampere hours of plating if Zero Discharge Recovery is used for the rinsing and ventilation systems. It will be considerably higher if Zero Discharge is not being employed.
Many hard chrome shops dont have in-house analysis capabilities, nor do they see the need for closer bath control. This is a huge mistake because maintaining the proper CrO3:SO4 ratio is incredibly important. Without this control, the deposit quality and, therefore, the profitability of the operation rapidly declines.
Old-school platers simply used a hydrometer to measure the Baumé (or density) of the bath as an indicator of the chromic acid level. This practice is wholly inadequate because the Baumé reading includes the impurities in the bath, like trivalent, iron, and copper. Therefore, the chromic acid level will always be lower than whats indicated by Baumé. This upsets the critical balance of the presumed chrome:sulfate ratio.
Another mistake is many job, and captive hard chrome platers solely rely on their suppliers to provide their bath testing needs. This is problematic on several fronts:
Our laboratory specializes in hard chrome bath analysis and receives samples from all over the United States and overseas. Experience over the past thirty years indicates many bath samples were sent to solve quality issues that related directly to the imbalance of the chrome:sulfate ratio. This wouldnt be the case if these shops had their own in-house analysis abilities.
As a minimum, a chrome shop should have the ability to test its chromic acid and sulfate levels in-house. The frequency of bath analysis is based on maintaining the desired chemical balance within 2%-5% limits, with a 2% plus-minus variance being the most desirable. Most operations will find that doing this once a week meets that requirement.
The equipment needed for an in-house laboratory isnt overly expensive relative to the benefits obtained. The space requirement isnt prohibitive either, and typically 4-5 bath samples can be run in an hours time once the operator becomes familiar with the procedures.
Higher production operations may also want the ability to test their secondary catalyst, trivalent, and impurities like iron, copper, and chloride. However, these tests require additional equipment and operational expertise. Normally, using an outside laboratory to check these items is workable as their levels dont change quickly, and the minor changes that do occur dont affect the plating quality. Thats not to say their concentrations can be ignored; quite the contrary, its just that having them tested monthly is usually adequate.
The task of taking a bath sample, doing the analysis, and making the bath additions should be delegated to a single individual. Using multiple employees for this invites confusion and potential problems. The best employee for this is frequently the lead shift foreman or the plating supervisor.
The old-school box-type test kits are inadequate for todays process control requirements. Professional laboratory equipment is more durable and provides the best results. Theres an enormous difference in the accuracy obtained between using a test kit and using a dedicated laboratory with professional-grade reagents, glassware, and procedures.
The in-house lab doesnt need to be overly large or complicated, but using a small enclosed room is best. An area of 10 x 10 is adequate if its just used to test the chrome and sulfate. Ideally, this would be located near the plating line but away from any polishing or machining operations, so the lab stays free of airborne debris. Ideally, this room would be air-conditioned. This lab setup doesnt need to be elaborate; all thats generally required is the following:
Its also recommended that bath samples be sent to an outside laboratory on a regular basis for backup analysis. This is needed to test the other bath ingredients as the catalysts used and to check the accuracy of your in-house chrome and sulfate tests. This laboratory should also test the impurity levels of chloride, trivalent, iron, and copper. Using a laboratory that specializes in hard chrome technology is highly recommended for this.
The frequency of having the backup analysis done will vary with the amount of work plated and the tank volumes. Most shops find that doing this monthly is sufficient. The goal is to track the impurity level build-up before they cause plating issues. This prevents the huge peak and valley quality swings that some shops experience. The result is producing top-quality deposits repeatedly from month to month and year to year. It can also eliminate or greatly reduce the volume of rework required.
The chloride level is critical because its a very powerful contaminant. It should always be below 50 ppm, and keeping it below 20 ppm is highly recommended.
Besides creating plating problems, these impurities also decrease the plating efficiency, which increases the plating time and the AC electrical costs.
The trivalent Cr level is also important, and it should be maintained around 1% (as a percentage of the hexavalent chromic acid); it becomes an impurity when its much higher than 2%.
Iron and copper impurities become problematic when above 5 g/l individually or 5 g/l total when combined. Actually, copper has a much stronger negative effect than iron, so it should be kept as low as possible.
One reason these impurities cause problems is they chelate (tie up) the hexavalent chromium, thereby throwing the usable sulfate ratio out of kilter. They also increase the baths electrical resistance, which requires either raising the voltage or using reduced amperage. Besides creating plating problems, these impurities also decrease the plating efficiency, which increases the plating time and the AC electrical costs.
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The best way to measure the combined effect of these metallic impurities is to determine the TCL level in the bath. TCL stands for Total Contaminant Level and is simply the sum of the trivalent percent plus the g/l of iron and copper added together. As an example, a bath having levels of 1.5% trivalent, 1.8 g/l of iron, and 1.2 g/l of copper would have a TCL of 4.5.
The only time a chrome bath is pure is when its first made up. Even then, its not truly pure, as there are trace impurities in the chromic acid and the water supply. Once made up fresh, the bath continually accumulates additional impurities as it used to plate parts. The rate of the impurity build-up is dependent upon several factors like the pre-plate finishing and cleaning, the reverse etching, the type of anodes and fixtures used, the location of the buss bars, and the stop-off techniques used.
The bottom line is these impurities can never be eliminated; they can only be controlled. This is done by reducing the TCL input as much as possible and then lowering it when they reach a predetermined level. Controlling the TCL is best done by first dummying the bath to reduce the trivalent and chloride and then decanting it (bath dilution) to lower the iron and copper levels.
Its the authors opinion that maintaining the TCL within the range of 4.8 7.2 provides the best option for maintaining high-quality deposits, lowering the rework rate, and increasing the overall efficiency and profits. This approach is significantly more efficient and less costly than using porous pots, ion exchange, or electrodialysis would be. Incidentally, porous pots do not remove iron or copper, and they are very inefficient for reducing the trivalent and chloride. Electrolytic dummying using a 20-30:1 anode ratio is the most efficient way to lower excessive trivalent and chloride levels.
As an example, a chrome bath sample was recently sent to our laboratory with the hopes of solving a major plating quality issue. It was a seven-year-old bath containing 5% trivalent and 23.2 g/l of iron and copper combined, giving it a TCL of 28.2. This is almost 4 times the recommended maximum TCL and equates to 348 pounds of tramp iron and copper dissolved in the 1,800-gallon solution. No wonder it couldnt plate anything successfully. Unfortunately, that bath had to be dumped and remade fresh as there was no economical way to salvage it. The high cost of replacing that bath put a very significant dent in that companys profits. Their high operational cost, poor quality, and loss of customer satisfaction could have been avoided had that shop just used better process control. A chrome bath thats properly operated and controlled will last well in excess of fifty years and still be capable of high-quality plating parts.
But you cant control your impurities, or other bath ingredients for that matter, without having a routine analysis done on the bath and its impurity levels.
However, many hard chrome platers dont make a serious effort to control their bath impurities, instead allowing them to build to a level that creates serious plating issues. At that point, they either stop using that bath or dump and remake, a very costly affair. Meanwhile, their quality, efficiency, and profits continually decreased, and they may have even lost a customer or two along the way. All that could have been prevented by simply maintaining their TCL between 4.8 7.2.
But you cant control your impurities, or other bath ingredients for that matter, without having a routine analysis done on the bath and its impurity levels. The TCL should be tracked over time so they can be dealt with when the TCL reaches 7.2. Thats why having the in-house capability to test the basic bath ingredients and then routinely using a qualified outside laboratory to check the catalysts and impurity levels is so important.
The cost for this service is offset many times over with improved plating quality, reduced rework, and much lower operational costs. Using an outside laboratory for backup testing and support shouldnt be considered an expense; its an investment in quality control thats repaid many times over with improved market positioning and increased profits.
Rework due to bath imbalances and excess impurities is a very costly affair because the part must now undergo stripping, refinishing, and replating. This cost is at least 3-times that of having plated it correctly the first time and likely even higher. This extra cost cant be passed on to the customer and must therefore be absorbed.
Hard chrome platers that control their bath ingredients within a 2%-5% variance and control their impurity TCL within the 4.87.2 range have much lower operating costs, higher production efficiencies, and reduced rework rates. These factors relate directly to increased profitability and even to their long-term sustainability.
21st-century Industry demands high-quality and on-time deliveries. One of the best ways to meet their objectives is to take control of the plating bath and keep it healthy. Platers who follow this concept will prosper while those ignoring it, well not so much.
All thats needed for this operational improvement is exercising better process control. The cost of doing this is greatly offset and repaid many times over. Its more than just a quality issue; its also logical and makes good business sense.
Eric Svenson Sr. is CEO of Plating Resources, Inc., in Cocoa, Florida. Visit www.plating.com or
When Mark took over National Plating in , it was time to either commit to big improvements or risk losing the business. For the Palik family, each generation had reacted to its times, applied its own philosophy and been successful in its own way.
It was a small shop at that time, with about eight employees. Mark's plan was clear: respond to this challenge and clean up its act. He immediately began to expand the business and within two years had tripled sales. Today, it employs 40 people.
How did he finance these early expansions? "Hard work," is his quick answer. "We've always had handy people and our own welders. It is not rocket science to build a plating tank. We even built a few of our own barrels at one time. Building your own equipment is a distinct advantage, not something many can do."
MARK PALIK checks the coating thickness using equipment capable of measurements within approximately 1%. The big leap forward. The decision to launch the new line was made two years ago. Business was good, and Mark again wanted to expand. Cost efficiency was the key philosophy behind this major move. "Where prices are going in this industry, it doesn't make sense for anybody with conventional equipment to tackle large volumes of work. We needed to build a line that was so productive and cost efficient that I could run work at the going rate."Like the movie Field of Dreams, Mark's theory was "If you build it, they will come." When people asked, however, if he had lined up work for this new line, he had to admit that he had not, but he did have two or three big accounts in mind. "There was no doubt in my mind that when we showed them we could turn massive volumes quickly with better QC and SPC levels than they were getting, they would at least give us an opportunity to be a second source," he explained. "That's all we would need to earn more of their business."
Has it worked? "Yes," he replied with a grin. "Although it was not as easyas I thought it would be." He knew that even with the ups and downs of demand in this business, any plater doing automotive work would have to meet that industry's tough ISO and QS requirements with the QC and SPC his company had in place.
He was right. This has helped attract new business. "Since we jumped on the large-volume bandwagon, our volume has increased over 300%, sales have doubled, and we were just getting started! We are running the line at about three-fourths capacity now and expect to hit full capacity by year's end. I do not know of any barrel plating line that is more productive."
Because the company did much of the work itself, Mr. Palik pointed out that the investment was probably half what it would have cost had it been engineered and installed by an outside firm. "Although there's no other U.S. barrel line quite like this," he said. "I visited a similarly automated one in Canada that cost more than $4 million."
Another philosophy Mark Palik has always employed is no third shift, even at the busiest of times. He feels that operating around the clock seven days a week cannot be done without sacrificing quality. "We run two shifts five days a week," he said, "eight to twelve hours per shift, depending on how busy we are, and always have available capacity. If we get too busy while running two twelves, we'll just run a Saturday and get caught up."
Features of the new line. Here are the key features that make this new zinc plating line unique and efficient:
Those plating shops serving the auto industry are facing a requirement that all Tier Two suppliers be ISO registered by year's end. Mark Palik sees that, too, as an opportunity. "We plan to be registered by then," he says. "We're half-way there already."
Although plating demand in the Cleveland area has slacked off since he committed to this new line, Mr. Palik remains optimistic. Once he convinced a few
big-volume customers that his small shop was moving into the big time, it didn't take long for the news to spread. "People started talking about the line and the job we were doing for them," he recalled. "Soon people I had called months ago started calling back. Our reputation started paying off." PF
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