Hardchrome stripping-What is hard chrome plating? - TWI

Chrome plating less commonly chromium plating , often referred to simply as chrome , is a technique of electroplating a thin layer of chromium onto a metal object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness. Sometimes, a less expensive imitator of chrome may be used for aesthetic purposes. There are many variations to this process, depending on the type of substrate being plated. Different substrates need different etching solutions, such as hydrochloric , hydrofluoric , and sulfuric acids.

Hardchrome stripping

Hardchrome stripping

Hardchrome stripping

Hardchrome stripping

In Hardchrome stripping projects Wikimedia Commons. Please enable JavaScript in your web browser. The formation of micro-porous chromium is achieved by a specialised plating method involving Hardchrome stripping use of inert suspended particles. Members' Portal. There are many variations to this process, depending on the type of substrate being plated. Not to be confused with Chromate conversion coating. Hard Chrome Plate Usually used to build up shafts or areas on steel that are subject to severe wear.

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Chemical Stripping In chemical stripping, the Simpson porn gallary to be stripped must be oxidized from Hardchrome stripping metallic state to an ionic state. The processes, chemicals and equipment, plus control and troubleshooting. Community See All. That explains why the HCl did nothing. Machine Tools: drills, taps, dies, extrusion screws and rolls are hard chrome plated to extend life and improve performance. Hi Chris, Hydrochloric acid will strip chrome, but it works best when there is brass underneath as it Hardchrome stripping not to attack that once the chrome has gone. A typical pretreatment cycle prior to metal stripping usually includes a 3—5 min soak in a hot alkaline cleaner Hardchrome stripping by thorough rinsing and cathodic activation in an electrocleaner. Firearms: interiors of gun barrels are hard chrome plated. This process quickly fell into disfavor when single-step, non-cyanide processes were developed. Sir, While stripping the Hardchrome plated coatings with HCl in chemical method, how to decide the stripping time when there is a vast variation in coating thickness, around 10 - 40 microns.

Chrome plating can be used for two purposes: A.

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Chrome plating less commonly chromium plating , often referred to simply as chrome , is a technique of electroplating a thin layer of chromium onto a metal object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness. Sometimes, a less expensive imitator of chrome may be used for aesthetic purposes.

There are many variations to this process, depending on the type of substrate being plated. Different substrates need different etching solutions, such as hydrochloric , hydrofluoric , and sulfuric acids. Ferric chloride is also popular for the etching of nimonic alloys.

Sometimes the component enters the chrome plating vat while electrically live. Various finishing and buffing processes are used in preparing components for decorative chrome plating. The chrome plating chemicals are very toxic. Hexavalent chromium plating solution is used for decorative and hard plating, along with bright dipping of copper alloys, chromic acid anodizing, and chromate conversion coating. A typical hexavalent chromium plating process is: 1 activation bath, 2 chromium bath, 3 rinse, and 4 rinse.

The activation bath is typically a tank of chromic acid with a reverse current run through it. This etches the work-piece surface and removes any scale. In some cases the activation step is done in the chromium bath. The chromium bath is a mixture of chromium trioxide CrO 3 and sulfuric acid sulfate , SO 4 , the ratio of which varies greatly between to by weight. The temperature and current density in the bath affect the brightness and final coverage.

Temperature is also dependent on the current density, because a higher current density requires a higher temperature. Finally, the whole bath is agitated to keep the temperature steady and achieve a uniform deposition. To overcome this problem the part may be over-plated and ground to size, or auxiliary anodes may be used around the hard-to-plate areas. In the U. The EPA lists hexavalent chromium as a hazardous air pollutant because it is a human carcinogen , a "priority pollutant" under the Clean Water Act , and a "hazardous constituent" under the Resource Conservation and Recovery Act.

Due to its low cathodic efficiency and high solution viscosity , a toxic mist of water and hexavalent chromium is released from the bath. Wet scrubbers are used to control these emissions.

The discharge from the wet scrubbers is treated to precipitate the chromium from the solution because it cannot remain in the waste water. Additional toxic waste created from hexavalent chromium baths include lead chromates , which form in the bath because lead anodes are used.

Barium is also used to control the sulfate concentration, which leads to the formation of barium sulfate BaSO 4. Trivalent chromium plating is an alternative to hexavalent chromium in certain applications and thicknesses e.

A trivalent chromium plating process is similar to the hexavalent chromium plating process, except for the bath chemistry and anode composition.

There are three main types of trivalent chromium bath configurations: [1]. The trivalent chromium-plating process can plate the workpieces at a similar temperature, rate and hardness, as compared to hexavalent chromium.

Plating thickness ranges from 0. Better throwing power means better production rates. Less energy is required because of the lower current densities required.

From a health standpoint, trivalent chromium is intrinsically less toxic than hexavalent chromium. Because of the lower toxicity it is not regulated as strictly, which reduces overhead costs.

Companies now use additives to adjust the color. In hard coating applications, the corrosion resistance of thicker coatings is not quite as good as it is with hexavalent chromium. The cost of the chemicals is greater, but this is usually offset by greater production rates and lower overhead costs.

Decorative chrome is designed to be aesthetically pleasing and durable. Thicknesses range from 0. The chromium plating is usually applied over bright nickel plating. Typical base materials include steel , aluminium , plastic , copper alloys, and zinc alloys.

Hard chrome tends to be thicker than decorative chrome, with standard thicknesses in nonsalvage applications ranging from 0. Unfortunately, such thicknesses emphasize the limitations of the process, which are overcome by plating extra thickness then grinding down and lapping to meet requirements or to improve the overall aesthetics of the "chromed" piece.

Modern "engineered coatings" do not suffer such drawbacks, which often price hard chrome out due to labor costs alone. Hard chrome replacement technologies outperform hard chrome in wear resistance, corrosion resistance, and cost. Rockwell hardness 80 is not extraordinary for such materials. Using spray deposition, uniform thickness that often requires no further polishing or machining is a standard feature of modern engineered coatings. These coatings are often composites of polymers, metals, and ceramic powders or fibers as proprietary embodiments protected by patents or as trade secrets, and thus are usually known by brand names.

Hard chromium plating is subject to different types of quality requirements depending on the application; for instance, the plating on hydraulic piston rods are tested for corrosion resistance with a salt spray test. Prior to the application of chrome in the s, nickel electroplating was used. In the short production run prior to the US entry into the Second World War , the government banned plating to save chromium and automobile manufacturers painted the decorative pieces in a complementary color.

In the last years of the Korean War , the US contemplated banning chrome in favor of several cheaper processes such as plating with zinc and then coating with shiny plastic. In , a Restriction of Hazardous Substances Directive RoHS was issued banning several toxic substances for use in the automotive industry in Europe, including hexavalent chromium, which is used in chrome plating. However, chrome plating is metal and contains no hexavalent chromium after it is rinsed, so chrome plating is not banned.

From Wikipedia, the free encyclopedia. This article is about a chromium electroplating technique. For other uses, see Chrome disambiguation. Not to be confused with Chromate conversion coating. Archived from the original on Retrieved Archived PDF from the original on 16 August Retrieved 3 May CHrome Corporation. Retrieved 16 August Paul; Black, J T. Materials Chemistry and Physics. Categories : Automotive styling features Chromium Corrosion prevention Metal plating.

Hidden categories: CS1 maint: archived copy as title. Namespaces Article Talk. Views Read Edit View history. In other projects Wikimedia Commons. By using this site, you agree to the Terms of Use and Privacy Policy.

Hi, Bruce. I am currently investigating the use of Tetra potassium Pyrophosphate TKPP for short to use in solution in a gallon tank to strip chrome by switching the current direction. They have fewer variables to be controlled and are less expensive to set up than their electrolytic counterparts. As such, control and preparation are usually minimal. Chemical immersion strippers require the least amount of equipment.

Hardchrome stripping

Hardchrome stripping. Applications of Industrial Hard Chrome:

Similar SermeTel topcoated systems have seen millions of hours of successful service in military, commercial aviation and industrial turbines. Thickness 0. SermaLoy J is a diffused slurry aluminide coating with a unique silicon-enriched outer layer. SermaLoy J is an intermetallic nickel aluminide with a silicon-enriched outer layer. The presence of silicon on the surface of the coating promotes the formation of a tightly adherent scale of very pure aluminum oxide Al2O3 that is very resistant to dissolution by the liquid sulfate salts that cause hot corrosion.

The excellent high temperature oxidation resistance of SermaLoy J is due in part to reduced oxygen mobility through the pure alumina as well as to the stabilizing effect that the silicon has upon the aluminde. Silicon in SermaLoy J also helps prevent thermal fatigue cracking. Any advice will be appreciated.

Hindsight, you would have been far better off to have masked the area before plate. It is a fairly heavy coat, so I think that whatever stripper will undercut the masking. If it were my problem, I would grind it with lots of fluid and a proper stone so that it does not burn or flake.

If you have to strip it, you might consider using brush techniques to electrolytically strip it. Best luck. I need to strip off a chrome bore plating from a rifle barrel. Not the whole bore, just the chamber area. This is in preparation for using a chamber reamer made of high speed steel HSS. I have driven a hard plastic nylon? I have access to both Hydrochloric acid and Sodium Hydroxide.

So which should I use? I will hold the barrel vertically, and pour the treatment solution in. Will the NaOH eat the chrome at room temperature?

The area needing stripping is eroded, and the chrome is in islands now, rather than being continuous, as it was when the bbl was new. Many thanks. Hi Chris, Hydrochloric acid will strip chrome, but it works best when there is brass underneath as it tends not to attack that once the chrome has gone. Your gun barrel will be made of steel, the chrome will not be removed evenly over the whole surface. Some areas will become bare before others, so the acid will carry on etching the base metal.

So that has to be considered. Also hydrogen will be impregnated into the metal making it brittle, something you don't want in a gun, unless you de-embrittle the gun afterwards. If you wish to use sodium hydroxide instead, then you will need a power supply to provide a DC current for etching, I. Sodium hydroxide alone will not do anything.

Is hot, strong caustic soda and DC anodic currents something that you are OK using? If not, employ a plating shop to do it for you. Good look Mark. Thanks very much Mark. Sounds like Caustic Soda is the way to go. Will a 12VDC car bty charger provide the current I need?

One side will be on the bbl, and the other will be a copper wire suspended in the NaOH hot solution? How hot does my NaOH solution need to be? And should I use a saturated solution? Thanks again from across the pond. Hi Chris, the Gun needs to be positively charged for it to be anodically etched. The solution will go yellow, this is Chrome VI, so you might want to consider safe disposal of that, as well as the neutralisation of the caustic after you are done.

Cheers Mark. Thank you. I have a strip of ceramic that has gold plating over chromium on it. I have to strip the gold and chromium for a customer without breaking the 0.

This strip is very fragile. Therefore, it cannot be sand blasted or even reverse current stripped. The gold was easy to strip. I already stripped the gold using Techni-Strip Au. My CRC handbook of Chemistry says that chromium is soluble in dilute hydrochloric and dilute sulfuric acids.

Neither solution has done anything to the chromium. Any suggestions? Good day Bruce. I really think that layer is not chrome. Usually the underlying layer under gold is nickel.

Maybe try a nickel stripper either sulfuric or cyanide based. I would be concerned about the ceramic substrate, if it will show signs of attack. Chrome is very passive, it will not accept any electrolytical deposition of metal. I have plated over chrome, and it is very difficult. Hope this helps. Our customer got back with us and said that the metallic coating is probably not chromium after all.

That explains why the HCl did nothing. Just send the parts back. I am currently investigating the use of Tetra potassium Pyrophosphate TKPP for short to use in solution in a gallon tank to strip chrome by switching the current direction.

Any ideas on how to start figuring out how long a batch would last? Hi Jose. I am not familiar with the use of this chemical for stripping chrome, and it sounds inexpensive and very environmentally friendly Therefore, I think what might determine its "life" is at what point do you want to treat the chrome as a batch, versus treating the chrome dragout in the rinse water? Everything came out fine except the rear brake pedals. There are two because I did two sets. At around the twelve minute mark the solution started bubbling much harder and began to turn dark.

I instantly pulled all the parts and rinsed them with water over an empty bucket. From the previous comment I know now everything but the brake pedals had nickel underneath. They are still very shiny, like someone said they should be. The brake pedals leached black sludge all over my gloves and they turned the water jet black.

Hardchrome plating - stripping

Hard chrome plating is an electroplating process in which chromium is deposited from a chromic acid solution. Various types of hard chrome include micro-cracked chromium, micro-porous chromium, porous chromium and crack free chromium.

The formation of micro-porous chromium is achieved by a specialised plating method involving the use of inert suspended particles. Porous chrome plating is developed by etching electrodeposited chromium. These are designed to retain lubricant, for sliding and bearing type applications. Chrome plating is used for wear and corrosion resistance in addition to its tribological low friction characteristics.

However, there are environmental concerns associated with disposal of the plating solution. This has led to many users of chrome plating seeking alternative coating methods. The HVOF sprayed coatings can offer superior wear and corrosion protection. Support for SMEs. Software Products. Go to Technical knowledge Search.

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Hardchrome stripping

Hardchrome stripping

Hardchrome stripping