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FREQUENTLY ASKED QUESTIONS
What is hard chrome plating?
How thick of a deposit can I get?
What advantage is there for me to use hard chrome?
What is the difference between decorative chromium plating and hard chromium plating?
What are the physical characteristics of plated hard chrome?
Is there a minimum number of parts that must be submitted at one time?
What information do you need to provide me with a quotation?
What kind of finish can I expect after plating?
Why do the edges of my chrome-plated parts have a heavier deposit?
What is a normal delivery time?
What is hard chrome plating?
Hard chrome is known and used throughout industry because of its wide variety of applications. It is often referred to as “industrial” or “engineering” chrome plating. The three most common uses are (1) part salvage on mis-machined or worn surfaces; (2) wear-resistance for parts subject to sliding motions; and (3) to improve tool performance and life.
How thick of a deposit can I get?
Although build-ups may be as heavy as 0.060 inches or as thin as 0.00001, we normally plate 0.0015 to 0.0025 inches thick over finish size when the part is to ground after plating. The thickness will be determined according to a specification required or by application. Thickness of the deposit is controlled by the amount of time the part is being plated. Thin deposits can be plated in a few minutes, whereas heavy or thick deposits could take several days.
What advantage is there for me to use hard chrome?
Factors that make chromium plating an excellent choice for tooling applications are (a) reduced friction, (b) its resistance to corrosion, (c) elimination of seizing and galling, and (d) minimization of wear. Tools that benefit from a chromium plate are drawing tools, punches, forming dies, cutting tools, steel or copper molding dies, plug gages, coining dies, and many others. Hard chromium plating is used in all types of industry, and almost any situation, where resistance to abrasion and wear is important.
What is the difference between decorative chromium plating and hard chromium plating?
The commonly known application for chromium plating is on steel automobile bumpers. This decorative chromium is applied over undercoats of nickel or copper and nickel. The final chromium deposit is usually less than 0.000050 inches thick; it is merely for appearance and to provide some tarnish resistance. In contrast, hard chromium deposits are intended to restore dimensions of under-sized parts or to improve resistance to abrasion, wear, corrosion or heat. Deposit thickness’ can typically range from 0.000050” to 0.020”.
Except under special circumstances, hard chromium plating is normally applied directly to the base metal. Heavier deposits are usually ground to a finish dimension after plating. Decorative chromium is used in the as-plated condition, or possibly buffed to enhance its shiny appearance.Uniformity of coating is another difference between decorative and hard chromium plating. Hard chromium deposits must be of uniform thickness, as parts are plated up to a finish dimension or ground to a finished dimension. In decorative chromium plating it is only necessary to cover the undercoat of nickel. Therefore, measures are not taken to assure a uniform thickness.
What are the physical characteristics of plated hard chrome?
Hardness - There are various methods for measuring hardness. A widely accepted hardness value is those obtained with the Vickers 136o diamond pyramid indenter or the Knoop indenter. The hardness test should be made on a carefully prepared and polished surface, preferably on a cross section of the plate, to eliminate any possible influence of the base metal on the hardness values obtained.
Chemical resistance - Chromium deposits withstand ordinary rust and corrosion. It also withstands corrosive atmospheres of most acids and caustics. A few chemicals will attack chromium, such as hydrochloric acid, some chloride salts, and hydrofluoric acid. Hot sulfuric acid also corrodes chromium severely.
Frictional characteristics - Hard chromium has a very low coefficient of friction, lending valuable resistance to sliding friction. A chromium plated surface tends not to seize, gall or cold-weld to another metal surface. These characteristics allow chromium to resist wear in applications where parts move in contact with other metallic parts.
Thermal expansion and conductivity - Chromium is a fairly good conductor of heat. It exceeds thermal conductivity of most metals except gold, copper and silver. Chromium has a low coefficient of thermal expansion. This makes it a good deposit for parts subject to extreme temperature changes such as forging dies.
Is there a minimum number of parts that must be submitted at one time?
No, we welcome high production jobs with thousands of parts, as well as the single piece. On small lot orders there may be a minimum charge.
What information do you need to provide me with a quotation?
For production jobs we prefer samples of the part so we can determine the method of fixturing. For other parts, usually a print or sketch is sufficient, with the area to be plated clearly marked. In addition to that; indicate the deposit thickness (per side) required and a finish dimension; whether the piece will be ground after plating; the number of parts; type of finish needed; and how soon you need the parts back. You can call us with this information or fax it.
What kind of finish can I expect after plating?
Generally, the finish we start with is the finish we end with after plating. Hard chrome plating tends to reproduce the same finish instead of improve it. Because of this, if the part is polished before plating, it maintains that same finish. If a “satin” finish is needed, we would normally lightly glass bead blast the part prior to plating. If the part has a very rough finish, as with cast parts, the chrome will not fill in holes, but rather emphasize the nodules.
Why do the edges of my chrome plated parts have a heavier deposit?
Because chrome plating is accomplished by the use of electrical current, sharp edges or protrusions tend to steal a disproportionate share of the current. Most of the parts we plate have special fixtures to facilitate accurate current delivery to the surfaces to be plated. While we make every effort to fixture the parts to avoid this problem a certain amount of it is unavoidable.
What is a normal delivery time?
Factors that effect delivery times are the number of parts, the chrome deposit thickness, the accuracy of deposit required, overall size of the parts, if there is a pre-plate process required, and the time of the day we receive it. Most single or small lot jobs are completed within 24 hours. For larger lots, you can expect turn around time of 2 – 3 days. | |
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