Understanding the term Galvanizing
“Don’t You Just Dip It?”
No.
This is a common question we hear regularly. While we wish electroplating were that straightforward, there are many variables which determine the proper procedures required to achieve a quality industrial finish. This can vary among finishes and is influenced by the individual characteristics of each part processed.
Understanding the Term Galvanizing
Galvanizing is a general term referring to the application of a zinc coating applied to steel for the purpose of corrosion prevention. It encompasses a variety of processing methods including Electroplating. Other galvanizing methods include Hot Dip Galvanizing, Thermal Spray, and Mechanical Plating. These are all methods for the application of an industrial zinc coating, but the procedures used, and characteristics of the final finish can vary greatly.
Electroplating, also called electrogalvanizing, is most often confused with hot-dip galvanizing. Both methods provide corrosion protection, but the application of the coating and performance of the finish are different.
Differences Between Electroplating and Hot-Dip Galvanizing
Hot-Dip Galvanizing
In hot-dip galvanizing parts are submerged into a thick liquid bath of molten zinc that creates a coated surface by bonding with the steel. Any area that is submerged will receive coverage including corners, inner dimensions, and recesses. Hot-dip galvanizing provides a thick, durable, long-lasting coating.
Electroplating
During electroplating, parts are submerged into an electrolytic solution activated by a direct current of electricity causing ions to transfer from a zinc anode onto the part. Only surfaces that are in direct contact with the current will receive plating which excludes areas such as recesses, tubing I.D., or blind holes.
Electroplating will provide a thin, uniform finish with minimal impact on dimensional tolerances. Its effectiveness against corrosion is sufficient in many applications.
Factors that affect the Electroplating Process
Overall, electroplating is a standard process. However, achieving a quality finish that exceeds expectations in both appearance and performance depends on the unique characteristics of each part.
There are many variables that affect the procedures we use to meet customer specifications and exceed quality standards.
1.) Type and Hardness of Base Material
Not all materials can be treated the same. The type of base material, including steel grade and composition, can greatly affect the amount of time required for a part to build adequate plating thickness. Base material also helps determine the necessary sequence of steps throughout the cleaning, plating and chromating phases.
High-strength or heat-treated steel with hardness of 39 HRC or higher is highly susceptible to embrittlement and may require baking after plating.
2.) Quality of Base Material
Achieving a high-quality appearance depends greatly on the condition of the base material prior to plating. Since electroplating will not fill-in or cover up imperfections, parts with pre-existing defects such as cracks, pits, scratches, die marks, etc. can be more visible after plating.
For the highest quality appearance, parts should be free of defects prior to plating.
Material quality can also influence which pre-treatment processes are necessary and the extent of their effectiveness. Electrocleaners are effective against heavy soil, grease and corrosion but may not clean heavy scale formed at the mill, during welding, heat treating, etc.
3.) Part Size and Geometry
Part shape and size determine whether parts are rack or barrel processed.
Barrel Plating
Small durable parts like fasteners are generally well-suited for barrel plating. Since barrel plating is a form of bulk processing it offers a cost-effective solution for turning around high-volume orders quickly.
Part shape should also be considered when choosing the type of processing. Light, flat parts can stick to each other during barrel plating causing voids or finish inconsistencies. Springs, hooks, and u-shaped parts can tangle easily also resulting in plating voids and may require significant handling to separate. Parts with these features may be more suitable for rack plating.
Rack Plating
Rack plating is used to process large, delicate, or complex parts that cannot be finished through barrel plating. Part size and geometry are important in determining the number of pieces that can be processed at once and the ideal racking configuration.
High current density areas like corners and edges will build plating thickness quicker than lower current density areas such as the middle of the part. Recesses and cavities typically do not receive plating coverage and are excluded from most plating specifications. Many variables need to be considered to achieve adequate coverage without over-plating.
4.) Special Features
Parts with special features including joined surfaces, blind holes, or movable components, are more susceptible to plating defects. To minimize the risk and effects of over-plating, bleed-out and air pockets, special handling may be required.
Noting these features during the quoting phase will help ensure desired results are achieved at an accurate cost.
5.) Customer Specifications and End-Use of Part
The intended use of the final product is critical when choosing the type of plating, chromate and thickness.
Parts used outdoors will require a more durable finish with higher wear resistance than components that are used indoors and protected from harsh conditions. Similarly, parts requiring secondary processing such as paint or powder-coating may have different specifications than parts with a single coating.
Understanding the plating requirements upfront can save time and cost from choosing the wrong finish.
Achieving a quality finish requires a tailored process to meet the needs of each part. While anyone can just “dip it”, a high performing finish goes far beyond just that.
Gatto Industrial Platers has the experience and capacity to consistently meet your expectations. Contact us today for a quote.