MIL-QQ-S-365 & ASTM B700

There are a few different kinds of silver that can be plated, which are separated by purity, hardness and finish. Silver purity fits into three different categories — type I, II and III. Hardness grades come in A, B, C or D. Engineering specifications for silver categorize this metal's finish within three different types, much like its purity.

Silver lends itself well to electroplating due to its unique properties, which are unlike many other metals. People have used this material for centuries across numerous industries — and for a good reason. The material's defining characteristics combine to create a metal that's durable, cheap and hardier than the rest when operating within diverse industrial applications. If you're looking for a cost-effective plating solution, silver is a top choice. By emphasizing quality and function, this metal has earned a valuable space among popular metals used for plating.

Silver Plating Specifications

When performing silver electroplating, it may be necessary to follow defined engineering specifications to get the best results. When manufacturing metal parts, you always want to get the most favorable outcome for your time and money. Learning and following the specs can help you accomplish that. There are two different standards:

1. ASTM B700

This set of specifications applies to silver electroplating used for engineering. It has replaced the federal silver standard, MIL-QQ-S-365. It includes a set of criteria for minimum purity, which looks like this:

• Type I: 99.9 percent silver minimum
• Type II: 99.0 percent silver minimum
• Type III: 98.0 percent silver minimum

The ASTM B700 also consists of a range of requirements concerning silver hardness and post-treatment procedures. It's similar to the QQ-S-365 in its criteria but more specific:

• Grade A: Matte — no brighteners in the plating solution.
• Grade B: Bright — brighteners placed in the plating solution.
• Grade C: Bright — Grade A silver that's received mechanical or chemical polishing.
• Grade D: Semi-bright — brighteners placed in the plating solution.
• Grade N: No chromate treatment.
• Grade S: Supplementary anti-tarnish treatment.

2. MIL-QQ-S-365

The ASTM B700 has replaced this federal standard, but many engineering organizations still use it, which makes it essential to know. This set of requirements outlines the finish types and hardness grades of silver:

• Type I: Matte finish
• Type II: Semi- bright finish
• Type III: Bright finish
• Grade A: Supplementary tarnish-resistant treatment
• Grade B: No supplementary tarnish-resistant treatment

This requirement also dictates that the thickness of silver plating must be at least 0.0005 inches, especially when using silver electroplating for functional reasons.

• Grade A: Matte, with no brighteners used in the plating bath
• Grade B: Bright, due to brighteners placed in the plating bath
• Grade C: Bright, due to chemical or mechanical polishing of Grade A silver coatings
• Grade D: Semi-bright, due to brighteners placed in the plating bath
• Class N: Receives no chromate treatment
• Class S: Receives supplementary tarnish-resistant treatment

Your products may also need to adhere to specific undercoating requirements. If you are silver plating a steel, zinc or zinc-based alloy surface, your product should have a nickel-over-copper undercoat. Silver plating on copper or copper alloy products requires a nickel undercoat.

Silver Plating FAQs

To better understand the silver plating process and how it can benefit your business, it helps to know the details of silver itself and how electroplating works. Here are some commonly asked questions about silver plating:

What Is Silver?

Silver is a precious metal commonly used in industrial manufacturing applications. Although it's prevalent within the metal finishing industry, it has a wide range of uses across very different sectors, including photography and mirror making. People have used it for hundreds of years as forms of currency, medications, decorative materials and much more. Scientists categorize silver as a noble metal, meaning it is resistant to oxidation — even at extreme temperatures.

What Are the Characteristics of Silver?

If you need a coating that will last a long time, silver is one of your best bets. Silver's noble classification speaks to its durable quality of being resistant to corrosion. Its high melting point makes it excellent for high-temperature applications, as it won't bend or melt in the face of extreme heat. It also holds up well in low-oxygen environments, which has made it a go-to for metal manufacturing in the aerospace industry.

When you choose the process of silver plating for finishing your metal parts, you can go for a matte, bright or semi-bright look. This versatility is appealing for business owners who prefer multiple options when plating onto their goods. Additionally, silver possesses high reflectivity and displays excellent photosensitivity, which has earned it a valuable place in the photography field.

Where Does Silver Come From?

Silver originates from silver mines, although a significant portion of it also comes from copper, zinc, gold and lead mines. Silver and gold are always found in nature together. Many miners collect silver from deposits filled with this material, but it often comes from other metal ores as a byproduct. Mexico and Peru are the largest producers of this noble metal. People create purified silver by using electrolysis to remove its impurities and any other traces of metal it contains.

Secondary silver also counts toward the total supply of this material. This type of silver originates from scraps, such as discarded electronics and photography gear. Other sources of the substance — like jewelry or coins — often go un-recycled because it's too difficult to extract.

What's the Silver Plating Process?

The silver plating process steps are relatively straightforward, although they differ depending on what type you're doing — barrel or rack plating. The basic strategy, however, goes like this:

• Inspection: Before electroplating, you should always check the part for imperfections — like cold shuts or sharp edges — and amend these issues before starting the process. Otherwise, the quality of the substrate will decrease, and this may cause problems for your customers.
• Pre-treatment: Complete any necessary treatments before plating onto your metal part. You should also do an under-plating of copper, nickel or both metals. Additionally, you can add a silver strike or an anti-tarnish coating if there's a particular effect you want to achieve. If you plate a layer of nickel or copper with a 0.0005-inch thickness, the silver should also be 0.0005 inches for a total of 0.0010 inches.
• Electroplating: Silver plating involves submerging the substrate into a bath of silver ions. After passing an electric current through the solution, the ions deposit onto the part's surface, coating it in your chosen metal — in this case, silver.

What's the Cost of Plating With Silver?

The process of silver plating tends to be more cost-effective than methods that utilize other types of metals because of the material's commonality. The price you'll pay for silver electroplating depends on a range of factors. You'll need to consider how many parts you're plating, how thick the coating is, how large the pieces are and which method you're using. Market prices for silver can fluctuate, which will also dictate how much your plating job will cost.

What Are the Benefits of Electroplating With Silver?

Due to the convenient, high-quality nature of this metal, silver electroplating offers a range of unique benefits. You'll find plenty of excellent reasons to use this method for the next set of metal parts you need to produce. Here are some of the advantages you can enjoy:

• Corrosion-resistant: If you need a substance that's resistant to corrosion, silver is one of your best bets. Adding this durable coating to your metal substrates means the part itself will also become resistant to corrosion, giving the most durable product for your money's worth.
• Conductivity: Silver possesses a high level of thermal and electrical conductivity, making it ideal for applications involving electricity and high heat. Aerospace engineers, electronics developers and automobile manufacturers often use silver for its conductive properties.
• Lightweight: Despite its durability, silver is lightweight and easy to manipulate. High solderability is essential when working with metal parts that will eventually join together. It's capable of imparting all of its best qualities even when applied in incredibly thin layers, such as 0.0003 inches thick.
• Antibacterial: This noble metal fights bacteria growth and resists harmful organisms that could otherwise harm the human body. This characteristic is crucial for a substance that enters or contacts the body in the form of medical devices like insulin pumps and stethoscopes.

What Are the Potential Drawbacks of Electroplating With Silver?

This metal can tarnish, which is why it's essential to apply an anti-tarnish coating if you want to retain the appearance of your product. This factor may not be a concern for some, but if it is for you, you can opt for a tarnish-resistant treatment during the process.

A loss of adhesion during the electroplating process isn't uncommon for any metal. This phenomenon is mostly due to the substrate's surface. There may be oils, particles or specific metal alloys present that interfere with the coating's effectiveness.

Like adhesion loss, dull spots can appear on the plating with any metal you use. These can arise due to various issues, such as an ion solution with the wrong temperature or interrupted distribution of the electric current. Choosing the right plating professionals will eliminate many of these concerns. Silver is a great metal to work with, but it isn't exempt from errors if the manufacturer doesn't manage it correctly.

What Are the Industrial Applications of Silver Plating?

Silver plating is common to numerous industries, including automotive, medical, electronics and telecommunications sectors. This metal's versatility enables it to serve effectively in multiple applications, from flatware to wearable medical devices. Many medical devices incorporate silver-plated elements, which add to their longevity and electrical conductivity. Silver's antibacterial qualities shine here — in a sterile hospital environment, preventing the spread of disease is vital.

You'll find many silver-plated materials in the renewable energy sector, too, which is becoming increasingly popular due to its sustainable benefits. Many companies develop solar panels, batteries and other clean energy products with silver coatings. Combining the sun's energy with the conductive properties of silver can create lower electricity costs for businesses and individuals alike.

What Are the Alternatives to Plating With Silver?

Silver isn't the only metal you can use for finishing. You can employ materials like gold, copper, platinum and palladium, which all tend to be more expensive than silver. Each has type has its advantages, disadvantages and specifications to follow. Gold plating is excellent for its conductivity and anti-corrosion properties, but this process better to use only if the extra expenses aren't a problem for your company.

Palladium works well as a component to alloys, and it can function as a catalyst in various industrial applications. Like silver, it's lightweight but still retains an adequate level of durability, making it suitable for smaller objects. This metal has a major presence in the dental industry, as manufacturers use it to develop products like bridges and crowns.

What Are Common Silver Electroplating Issues?

Silver electroplating is an effective process, but it can occasionally pose some issues, depending on how the manufacturer does it. For example, you should only perform silver electroplating on your substrates after you've completed all pre-treatments, such as machining, soldering, welding or performing heat treatments.

If there are any imperfections like cracks or hydrogen embrittlement, these will cause problems during the silver plating process. Gaps in the coating coverage and poor adhesion are a couple of dilemmas you may encounter if the metal part doesn't receive proper treatment beforehand.

Troubleshooting Silver Plating Issues

You don't have to let common silver plating issues discourage you from trying the process. You can solve these with some troubleshooting techniques:

• Complete your treatments: Always complete all of your thermal and mechanical treatments before plating onto your product. Be sure to use easily removable lubricants during pre-treatment. Taking these precautionary steps reduces the chances of defective goods traveling to your customers, and you'll save time from needing to recreate more substrates.
• Avoid sulfur: When sulfur comes into contact with silver, it creates tarnishing. This substance is the main cause of this reaction. If you don't want your materials to lose their sheen, pack your finished products using silver saver paper and other non-sulfuric elements.
• Tell the manufacturer: If there are specific alloys on your substrate that may call for a different electroplating process, inform the manufacturer. They'll have a better idea of how to handle your part and give it the correct plating strategy to preserve its function.

Learn More About the Process of Silver Electroplating With SPC

Silver plating can give you a world of benefits when the technique is handled with care and precision. From excellent conductivity to lower expenses, there is a range of advantages that you can't always get with other metals.

At SPC, we provide the level of accuracy and care required to create an outstanding product. Learn more about the silver plating process by contacting SPC for a free quote for your next manufacturing job. We can help you select the best plating method for your industrial needs, ensuring high-quality and durable results each time.