From decorative etching to industrial and commercial applications, hard chrome coating is highly sought after due to its durability, versatility, and highly protective benefits. In this overview, we’ll dissect the two prevalent hard chrome plating processes, explain the benefits of thin dense chrome over other hard chrome plating applications, and discuss the required controls, industry specifications, and critical expertise that made Armoloy the gold standard in thin dense chrome coatings.
How does the chrome plating process work?
Chrome plating creates a thin layer of chromium on metal tools, equipment, and parts, with the goal of minimizing damage and extending their life.
The two main hard chrome plating processes are Hexavalent chromium plating and Trivalent chromium plating. Both processes involve placing a base metal into an electrolyte salt bath vat that contains different chemicals (chromium trioxide and sulfuric acid for Hexavalent chrome) where it warms to solution temperature. The plating is then applied for a period of time, so it attains the right amount of thickness required. For example, Armoloy’s thin dense chrome plating is applied much more slowly than traditional hard chrome plating, resulting in greater density and hardness exceeding 70 HRC vs. 65 HRC.
While it is the less toxic and more environmentally of the two, Trivalent chrome has seen more success in decorative vs. industrial purposes. An article in Finishing and Coating (November 2022) provides a comprehensive comparison of both processes, with Hexavalent chrome outperforming Trivalent chrome across a variety of factors.
Looking at deposit properties specifically, Hexavalent chrome has an excellent track record for hardness, ductility, adhesion, lubricity, wear resistance, and corrosion resistance.
In contrast, little is known about how Trivalent chrome performs across most of these parameters and has yet to see improvements in the functional chrome coating applications. In terms of hardness and adhesion, we do know that Trivalent chrome deposits are softer and weaker, impacting wearability. Macro cracking is also common. Wear resistance and corrosion resistance are also poor. In fact, for many applications, Trivalent chrome shouldn’t be placed directly on stainless steel; rather, it requires a nickel underlayer. As a result of these factors, Trivalent chrome is less than ideal for most industrial applications.
What are the benefits of thin dense chrome plating?
For OEM engineering and design purposes, thin dense chrome has all of the high-performance benefits of hard Hexavalent chrome—harness, wear prevention, low coefficient of friction—but with additional anti-corrosive properties.
Why? Hard chrome is thicker (from 0.0008 to 0.0050 in.) than thin dense chrome (0.0002 to 0.0006 in.). Therefore, large cracks and porosity are common on surfaces coated with hard chrome; large, exterior, easy-to-access surfaces are best suited for hard chrome applications.
In contrast, thin dense chrome is not a micro cracked deposit, and therefore, doesn’t have the porosity and cracks found in conventional hard chrome plating. The high degree of uniformity and versatility that thin dense chrome provides reduces the post grinding and honing common in sizing processes. Finally, the lower deposit thickness also minimizes buildup and dimensional changes, making it ideal for interior, hard-to-reach areas where precise tolerances are paramount and part balance is necessary.
As a result, thin dense chrome is the top choice for mitigating metal failure problems and improving repair and maintenance outcomes. Armoloy offers an engineered thin dense chrome coating technology rather than simply a plating, and we’re able to customize our coatings to our clients’ exact specifications.
Properties and Benefits of Thin Dense Chrome
| Properties of Thin Dense Chrome | Related Benefits |
| Adhesion (atomic, absolute bond) | Thin dense chrome is resistant to chipping, flaking, and peeling. |
| Hardness (up to 72Rc) | There are fewer cracks, inclusions, voids, and other surface irregularities with thin dense chrome vs. hard chrome. Other benefits derived from hardness include reduced wear rates, a reduced coefficient of friction, and high resistance to oxidation. |
| Lubricity (as low as .09 CoF) | A “dry lubricant” surface reduces friction. |
| Protective | Thin dense chrome provides prolonged corrosion protection—even when compared to stainless steel. It’s also hydrophobic and abrasion- and wear-resistant. |
| Precise | A precision layer of thin dense chrome eliminates costly and time-consuming traditional hard chrome plate and grind operations. |
| Versatile | Thin dense chrome can treat metals such as Aluminum, Beryllium Copper, Brass, Bronze, Copper, Inconel, Monel, and Steel (including Aircraft Steel, Cold Rolled Steel, Stainless Steel, and Tool Steel). |
What are the important thin dense chrome plating specifications?
Armoloy has spent decades innovating and refining our thin dense chrome plating process. Our ISO 9001:2015 certification verifies our compliance, and various sensitive industries, including medical and food processing and packaging, approve our thin dense chrome plating. Our Innovation and Process Development Center’s subject matter experts work with new application inquiries to ensure proper documentation and certification.
Plating specifications:
- AMS 2438: Requirements for thin, hard, dense electrodeposited chromium plating on surfaces of ferrous and nonferrous alloys.
- AMS 2460: Requirements for electrodeposited chromium plating.
- BAC 5709: Requirements for hard chromium plating
- USDA Approved
- FDA Compliant
Measuring and testing specifications:
- ASTM B117. Salt spray (fog) testing
- ASTM B571: Metallic coating adhesion testing
- ASTM F519: Hydrogen embrittlement of steel parts testing
- USP 10993-6, USP 10993-10, and USP 10993-11: Biocompatibility testing
Armoloy: 9 different ways to process thin dense chrome
Over the years, we have developed and refined our coating technology, giving Armoloy a distinct advantage in the marketplace—few conventional plating products can compare. Armoloy provides a full range of thin dense chrome surface coatings, including:
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- Armoloy TDC: A precision nodular thin dense chrome coating effective at deposits as low as .000050″, Armoloy TDC eliminates the need for secondary machining operations after plating.
- Armoloy XADC: This nodular thin dense chrome coating has the addition of a synthetic diamond composite, which enables coated parts to run nearly 20% cooler, thus enhancing wear prevention properties.
- Electrolizing® TDC: The gold standard of coating technologies for industrial applications, Electrolizing® TDC is a proprietary composition of pure chromium that produces a very hard surface.
- Bi-Protec A®: Composed of Armoloy TDC plus a nickel base layer, Bi-Protec® is excellent for highly corrosive applications.
- Bi-Protec X®: Composed of Armoloy XADC plus a nickel base layer.
- Gullon®: Armoloy Nodular TDC combined with solid-film coatings.
- AL-COAT®: Primarily for medical instruments, AL-COAT® is Electrolizing® TDC engineered for aluminum deposits. AL-COAT® is a precise, biocompatible, pure metallic chromium coating.
- BIO TDC: Biocompatible Nodular TDC for surgical, medical and beyond.
- ME-92®: Designed for the medical industry, ME-92® is Electrolizing® TDC formulated for medical grade and appearance options. ME-92® is an exacting, biocompatible, pure metallic chromium medical equipment coating.