FIGURE 3: Thermal Spray Powder Forecast, Chrome Replacement, Oil and Gas Sector
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FIGURE 4: Thermal Spray Equipment Forecast, Chrome Replacement, Oil and Gas Sector
FIGURE 2: Hard Chrome Target Market Forecast, Oil and Gas Applications
FIGURE 1: Worldwide Chrome Plating Demand, Hard vs. Decorative,
Providers of hard chrome electroplate, a relatively small but critical component of the overall chrome plating market, have endured tremendous stress and changing market forces in the past decade. As a result of changing health and environmental regulations, many shops that provide both decorative and hard chrome plate were forced to leave the business or move operations out of the United States. Hard chrome, used in critical applications such as aircraft landing gear and oil well equipment, is impacted by both adverse economic conditions, increased regulation and the emergence of competing coating methods.
Yet, as shown in a study by Thintri, Inc., the overall chrome plating industry is surprisingly robust. While the movement of plating operations overseas continues, for many plating shops, the difficult times appear to have passed and providers are optimistic about the future. However, for hard chrome, and to a lesser extent decorative chrome, competing technologies promise some erosion of markets late in the current decade.
Health Effects and Legislation
Chrome plating usually makes use of hexavalent chromium. Hexavalent chromium has long been known to be hazardous, but studies in the last decade have shown it to be particularly dangerous, especially for workers in chrome plating facilities.
In response to growing health concerns, the U.S. Environmental Protection Agency (EPA) began to regulate emissions into the air of chromium, citing strong evidence that hexavalent chromium causes lung cancer and other serious conditions.
The regulations focus on reducing the fine mists formed by electroplating, which is where most of the health hazards from hexavalent chromium arise. Methods recommended to reduce worker exposure to hazardous mists included use of scrubbers, mist eliminators, fume suppressants and others.
The apparently abrupt, and to some arbitrary and draconian, imposition of such stringent rules was something of a shock to the domestic chrome plating industry. A number of plating shops, many of them small, family-run businesses that had changed little for generations, could not afford to comply with the new rules and went out of business, perhaps more than half of those in the US. Many larger shops moved operations to Mexico or overseas, often to Asia, where environmental laws are less strict.
The chrome plating industry has survived by adapting to a new political environment. For many platers, cooperation with the new rules meant a complete overhaul of existing processes and facilities. Newly available technologies have allowed chrome plating facilities to function with enormously improved efficiencies and safety, and even enhanced productivity.
The trauma wrought by the regulations has faded, and the industry has reached something of a steady state. While there remains a movement of plating operations out of the country, other facilities are still shutting their doors and many in the industry complain about the difficulties of doing business, those facilities that survived the transition are, in many cases, running quite profitably. The North American chrome plating industry is, in many respects, surprisingly healthy. Chrome plating industry experts who were interviewed for the Thintri study were generally quite confident in the future of their business and did not feel threatened by alternative coating technologies.
In addition, the legislative environment has stabilized as well. While there may be new regulations to come from the Occupational Safety and Health Administration governing hexavalent chromium emissions in plating facilities and workers' exposure levels, and Japan and the Scandinavian countries are reported to have comprehensive bans on hexavalent chromium under consideration, there appear to be no near-term legislative initiatives that will significantly affect the ability of domestic chrome platers to function profitably.
Compared to its would-be replacements, chrome plating is still effective for many purposes. It is inexpensive, and can easily be performed in large batches. It is also foolproof, unlike competing plating methods that require multiple steps with complex chemistries.
Hard Chrome Market Forces
Hard or functional chrome plate comprises less than a quarter of the overall hexavalent chrome plate market (Fig. 1).
Hard chrome markets include wear resistant surfaces in aerospace, oil and gas, heavy equipment and a range of general industrial applications. Hard chrome plate is also used in restoration of dimensional tolerances, as in gas turbines where shafts require precise tolerances that may be off-target as a result of wear or manufacturing defects.
Hard chrome's desirability arises from its combination of adequate performance, with its low cost and ease of application. Chrome plating has been in use for a long time because it offers good coatings, both decorative and functional, with good properties and wide applicability, at low cost. No competing technology can really claim the same combination of performance, range of application, ease of processing and low cost.
It was precisely because of chrome's satisfactory performance that alternatives to chrome plate never received much attention until the safety and environmental push began. As legislation to control chromium pollution began to take effect, many large companies that made use of chrome plating, either out of a desire to avoid future legal problems or merely to act as good corporate citizens, made a commitment to reduce or eliminate the use of chrome plating within a period of years. In the process of investigating and developing alternative technologies, many users found good reasons to replace chrome plate in their applications beyond the simple cost and pollution issues. They gradually became aware that for specific applications, there may be substitutes that perform better than chrome plate at a comparable or even lower cost.
Chrome plate offers properties that are generally good. Still, the material offers limited hardness and corrosion resistance. If not properly applied, it can suffer from pitting, spalling, and other failures under stressful conditions.
Another problem with chrome plating is the relatively slow rate of deposition. Deposition rates in chrome plating range from four to eight microns per hour, compared with thirty microns per hour for nickel plating. Chrome processing also requires lengthy bakes following deposition. Because electroplating is a directional process, chrome coatings tend to be thicker on corners and edges, and tend to have little accumulation in recessed areas (which often can be overcome by use of conforming anodes). Lack of coating uniformity is a chief reason for follow up machining to meet dimensional tolerances.
Some parts used in demanding applications, including hydraulic rods, may have to be plated three or four times to obtain a thick, hard coating, compared with just once for an alternative technology like thermal spray.
Cost of ownership is a big complaint with hard chrome users. There is a significant need for coating processes with shorter processing time that give longer maintenance cycles.
Many experts interviewed across a range of industries in the Thintri study confirmed that their search for alternatives began out of concern for safety and the environment. However, having awakened to the superior performance of some alternatives, many users of alternatives now claim that even if all the health and environmental concerns about chromium could somehow be removed, there was no possibility of going back to their old coating processes.
While the chrome plating industry is large, stable and in no way threatened in its existence, for a number of specific applications, alternative technologies have already proven their value. In the long run, hexavalent hard chrome's dominance in many prominent applications is under threat.
Emergence of Competing Technologies
A number of coating techniques have emerged that may pose a threat to hexavalent hard chrome. While some remain in the development stage, others have already begun taking market share away from chrome plating.
Plating options include electroless nickel plating, electroless nickel composite plating, electrodeposited nanocrystalline alloys, and a few others. Trivalent chrome, which uses similar processing methods to hexavalent chrome but without most of the hazards, has already made serious inroads in decorative chrome markets. In the long run, a hard trivalent chrome coat may provide an alternative to hexavalent chrome that would allow chrome platers to maintain their client set in critical wear coating markets. To date, however, there is no satisfactory hard trivalent chrome process, but a number of companies and consortia in the U.S. and Europe have initiated development efforts.
Other methods, mostly in the development stage, include explosive bonding, laser cladding, physical vapor deposition, and electrospark deposition.
In the current decade, the greatest threat to the dominance of hard chrome is thermal spray. In each of the 14 or so forms of thermal spray, metal in powder or wire form is heated to melting and accelerated to the surface to be coated, building up to form the desired thickness. A major advantage of thermal spray is that a wide range of coating materials can be used, allowing coatings customized for individual tasks. Thermal spray coatings can be extraordinarily hard with great wear or corrosion resistance and up to a quarter inch thickness. Turnaround times with thermal spray are also low, with processing times as little as a fifth that of hard chrome.
The form of thermal spray that represents the greatest commercial threat to hard chrome is high velocity oxy-fuel (HVOF). HVOF accelerates metal particles at a relatively low temperature but high velocities onto a surface, forming coatings that are literally forge-welded to the substrate. Coating densities with HVOF can approach 100 percent, meaning there is little or no porosity. Respondents interviewed in the Thintri study indicated a solid consensus that HVOF coatings applied in wear applications provide superior performance in most situations compared with chrome.
The weakness of thermal spray is generally considered to be cost. Thermal spray is applied most often by a robot, which must be programmed for the part in question and must make frequent adjustments for parts with complex geometries. Unlike chrome plating which coats an entire surface at once, thermal spray is usually applied to an area about three quarters of an inch wide at one time. For large, simple surfaces, HVOF can often be applied more cheaply than chrome plating, but for complex geometries, HVOF processing is considerably more expensive than hard chrome. However, given the fact the HVOF coatings perform better and last longer than chrome, savings often accrue in the long term. In any case, the greater up front cost in applying HVOF has deterred many potential users.
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Another important limitation of all forms of thermal spray is that it is a line-of-sight technology. For parts that lie outside the line of sight, such as inner diameters below a couple of inches, other coating methods must be used. In aircraft applications, for example, the difficulty with applying thermal spray to inner diameters will mean that the penetration of thermal spray in aircraft applications will be limited to 80 percent in the long term. The remainder may stay with hard chrome, at least for most of this decade.
Case Study: The Oil and Gas Sector
The oil and gas sector provides a harsh test for functional surfaces. Drilling and pumping equipment is routinely exposed to aggressive brines, acids and gasses. Parts requiring durable surfaces include valves, chokes, blowout preventers, mud pumps, sucker rods, heat exchangers and separators, packers, safety valves, and all types of downhole tools.
The "oil patch" was an early adopter of thermal spray as a chrome substitute, particularly HVOF, which has been in common use in that sector since . For some parts, such as compressor rods, HVOF is already the dominant coating method. Other parts that are suitable for thermal spray include ball valves, hydraulic cylinder rods, mandrels and risers and tensioner rods for offshore rigs. There is also a large amount of thermal spray used in the industry that has nothing to do with chrome replacement.
Oil well equipment may be considered a less critical application area than aerospace, but it is certainly one of the most demanding. Drills must penetrate thousands of feet of earth and rock, often after going through thousands of feet of salt water. A drill ship might be 1,000 feet long, with tensioner systems that have to pull risers two miles long, each about three feet in diameter. Pinion shafts spin at high speeds, requiring high pressure lubricants, which can become a problem for coatings that aren't dense enough.
Because of the enormous size of many of the parts involved, the oil industry was sensitive early on to the high costs of thick chrome plate. With the emergence of thermal spray as an option, chrome plating often cannot compete economically.
Target hard chrome markets (i.e., those hard chrome applications that could reasonably be replaced with alternatives like thermal spray) in oil and gas applications are sizable, even though growth has stalled in the current economic climate (Fig. 2).
In the words of one industry participant, "these days chrome is a failure." The oil & gas sector is thus expected to adopt thermal spray technology, in particular HVOF, to replace hard chrome at a rate much higher than growth in the underlying target markets. The result will be greatly accelerated sales of thermal spray and equipment, even in a sluggish industry (Figs. 3 and 4).
The trend in oil and gas is typical of many other industries. Even during depressed business conditions, the switch away from chrome and toward alternatives like thermal spray will boost growth rates for those alternatives far beyond any growth in underlying target markets.
Hard Chrome Market Evolution
There remain serious concerns about the economic competitiveness of chrome alternatives like thermal spray. However, in most industries that make significant use of hard chrome, the transition away from chrome has already begun. Many businesses that use hard chrome have already set up thermal spray facilities, or have already prepared plans to do so. In several large applications, users have implemented plans that will result in replacement of 20 percent of hard chrome with thermal spray within two to three years, and up to 80 percent replacement by or shortly thereafter. While hard chrome markets are stable in the near term, by the end of the decade, serious erosion in those markets can be expected. The same pattern will be repeated in decorative chrome markets, although with somewhat less impact by alternatives.
Many providers of hard chrome plating services appear unaware, or unconcerned, about the long term threat posed by alternatives. Instead they are preoccupied by short term issues such as regulatory compliance. However, according to the Thintri study, the business landscape over the course of the present decade could change substantially in ways beyond chrome's health and safety issues.
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.
Eric Svenson Sr.Our goal is to help the industry because hard chrome is a critical process that&#;s vital to our economy and our national security. Although this is directed towards hard chrome operations, it also applies to all electroplating processes, whether they&#;re 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 today&#;s 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 that&#;s not generally recommended.
"An unhealthy plating bath always produces poor-quality deposits, has higher reject rates, and increases production costs."
It&#;s 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 it&#;s the lifeblood of the operation.
That&#;s not to say the other baths aren&#;t important because they are. It&#;s 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, it&#;s one of the most forgiving of all the plating processes. But that doesn&#;t 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. It&#;s 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 isn&#;t consumed during electrolysis. Its concentration only increases from drag-in or from bath additions. The sulfate level never decreases; naturally, it&#;s 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 don&#;t 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 what&#;s 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 wouldn&#;t 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 isn&#;t overly expensive relative to the benefits obtained. The space requirement isn&#;t prohibitive either, and typically 4-5 bath samples can be run in an hour&#;s 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 don&#;t change quickly, and the minor changes that do occur don&#;t affect the plating quality. That&#;s not to say their concentrations can be ignored; quite the contrary, it&#;s 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 today&#;s process control requirements. Professional laboratory equipment is more durable and provides the best results. There&#;s 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 doesn&#;t need to be overly large or complicated, but using a small enclosed room is best. An area of 10&#; x 10&#; is adequate if it&#;s 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 doesn&#;t need to be elaborate; all that&#;s generally required is the following:
It&#;s 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 it&#;s 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 it&#;s 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 bath&#;s 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.
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 it&#;s first made up. Even then, it&#;s 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.
It&#;s the author&#;s 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 couldn&#;t 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 company&#;s 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 that&#;s properly operated and controlled will last well in excess of fifty years and still be capable of high-quality plating parts.
But you can&#;t 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 don&#;t 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 can&#;t 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. That&#;s 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 shouldn&#;t be considered an expense; it&#;s an investment in quality control that&#;s 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 can&#;t 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 4.8&#;7.2 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 that&#;s needed for this operational improvement is exercising better process control. The cost of doing this is greatly offset and repaid many times over. It&#;s more than just a quality issue; it&#;s also logical and makes good business sense.
Eric Svenson Sr. is CEO of Plating Resources, Inc., in Cocoa, Florida. Visit www.plating.com or
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