Polishing (Electro-, or hand polish)

As our company name indicates, polishing and buffing services are an important part of our business. Although much of our business revolves around science and chemistry, hand polishing is considered both a skill and an art form. We are one of the few firms that remain offering ultra-high-quality hand-polishing services for all types of metals. Some of our talented craftsmen have been with us for more than twenty-five years. Hand polishing ensures customized attention on every job. Our skill and pride shines through every job.

Hand polishing and buffing services:

Craftsmen skilled in the art of hand buffing and polishing take years of training to perfect their craft. 

There is a great amount of skill and knowledge required to safely polish copper, brass, chrome, stainless, aluminum, or just about any metal part. Our craftsmen know precisely what it takes to create the perfect finish. We use many compounds and rouges in concert with our buffing machines to smooth a workpiece’s surface and obtain a brilliant shine. 

Proper buffing and polishing will remove minute surface imperfections caused by impurities, or by the manufacturing process without damaging the part. It takes skill, experience, patience, and attention to detail to provide excellent results.

Trust “Reliable Plating and Polishing” for your most critical polishing needs.

The Science of Electropolishing

Much of our business revolves around science and chemistry. Electropolish gives a shiny surface to (metal) using electrolysis. Electropolishing, also known as electrochemical polishing or electrolytic polishing (especially in the metallography field), is an electrochemical process that removes material from a metallic workpiece. It is typically used to polish, passivate, and deburr stainless parts. It is often described as the reverse of electroplating.

What we offer:

Hand polishing and buffing services and Electropolishing services.

Electropolishing is usually used for stainless alloys but can be used on many metals. Chemical electropolishing gives an assortment of finishes to choose from.

Size limitations:

Reliable Plating’s electropolishing services can create a bright or matte finish on products up to six feet in length.

As with all our services, we are happy to help you decide which process is right for your job.

The Polishing Process and Surface Roughness (Ra)

Polishing is a process of abrasion and refinement aimed at transforming a rougher surface into a smoother one by removing material and averaging out the peaks and valleys. The goal is to gradually reduce the “Ra” value to meet the specific requirements for the part’s intended use. Very often, the Ra number will be specified on the part drawing from the engineer, along with details like the grain direction or actual samples to match to. That’s where our talented polishers come in.

Types of Polished Finishes (indicated by an Ra #)

• Satin/Brushed Finish (#4):

A popular, matte finish with a fine, unidirectional grain, providing moderate reflectivity and good resistance to fingerprints and scratches. 

• Mirror Finish (#8):

A highly reflective, smooth, and mirror-like finish achieved with extensive polishing, requiring the most effort. 

• Non-Directional Finishes:

Lacking visible lines, these finishes are produced through methods like sandblasting or tumble finishing and can provide a uniform, smooth surface. 

Key Specifications

• Surface Roughness (Ra):

A quantitative measure of the surface’s smoothness. For example, a #4 finish may have an Ra value around 32 Ra, while a super-finish can have a single-digit Ra value. 

• Directionality:

Specifies whether the polished surface should have visible, parallel lines (directional) or be free of any discernible grain (non-directional). 

• Polish Standard:

Industry-specific finishes like the #4 pharmaceutical finish or #8 non-directional finish provide clear, standardized requirements. 

Factors to Consider

• Intended Use:

For cosmetic applications, a high-sheen mirror finish might be desired. For industrial parts, a satin or #4 finish might be more practical for its durability and ease of cleaning. 

• Subsequent Processes:

A finish specified for subsequent painting or powder coating may be less refined, as the added coating will cover imperfections. Some coatings require a certain amount of “tooth” on the surface for better bonding.

• Material:

Different metals, such as stainless steel or aluminum, have specific standard finishes suited to their properties. 

Achieving a Polished Finish

1. Sanding: Begin with coarse-grit abrasives to remove material and prepare the surface, progressing to finer grits for greater smoothness. 
2. Buffing: Use a wheel or pad with a polishing compound to further smooth the surface and increase reflectivity. 
3. Sand-blasting, Glass-bead, or Tumbling: Are a few of the different methods to achieve non-directional, smooth finish. 

Surface Roughness (Ra) 

Ra measures a surface’s average deviation from its ideal form, with lower Ra values indicating a smoother, less varied surface. In polishing, achieving a target Ra value is crucial for properties like reduced friction, improved corrosion resistance, enhanced hygiene in food and pharma industries, and a better aesthetic. Polishing reduces the peaks and valleys on a metal surface until the desired Ra is reached, making the surface suitable for its intended application. 

Definition of Surface Roughness (Ra)

• What it is:

Ra stands for “Roughness Average” and is a common, quantitative measure of a surface’s texture. 

• How it works:

It calculates the average height of the peaks and valleys on a surface. 

• Interpretation:

A lower Ra value signifies a smoother surface with less variation in height between peaks and troughs. 

• Units:

Ra values are typically expressed in micrometers (µm) or microinches (µ-in). 

Applications of Ra in Polishing Metal Parts

The specific Ra value achieved through polishing significantly impacts a part’s performance and aesthetics: 

• Functional Properties:
• Friction and Wear: Polishing to a lower Ra reduces friction between moving parts, which is vital in components like engine blocks or pumps. 
• Corrosion Resistance: A smoother, polished surface provides fewer sites for corrosion to start, extending the lifespan of metal parts. 
• Hygiene and Cleanliness:
• In the food processing and pharmaceutical industries, polished surfaces with low Ra values (e.g., Ra 20) are essential for preventing bacteria buildup and ensuring a hygienic environment. 
• Aesthetics:
• For consumer products or decorative pieces, a polished, low Ra finish provides a desirable, smooth, and visually appealing appearance.