Did you know that most springs require plating or finishing for both cosmetic reasons and to prevent rusting? Today, we have endless choices when it comes to spring surface treatment, but only a few of them are common.
On the other hand, most mechanical springs are still manufactured using spring steel due to its low cost. This is the primary reason why you will need some coating/finishing to be applied in the spring to provide some degree or corrosion protection.
Although this may take up the overall cost of the spring, it is much better than working with uncoated spring. Here are some of the common finishing and coating options in mechanical springs.
Organic Zinc Flake Coatings
Zinc flake coatings provide excellent corrosion resistance with zero risks of hydrogen embrittlement. The organic zinc flakes mainly consist of flakes of zinc in a unique suspension of resin that can be applied to the spring by spraying, dipping, or spinning.
Most custom spring manufacturers recommend using this finish where the consequences of spring failure may be severe. However, it is good to note that the cost of organic zinc coatings is a little higher compared to the price of other coating methods.
This is one of the most common types of spring coating used in precision spring design. The two most notable benefits of electroplating are low cost and effectiveness.
During electroplating, a lot of hydrogen is formed, and some of it may get absorbed into the steel surface. The absorbed hydrogen will soon render the steel fragile and subject to failure. To avoid this problem, the spring must be heat immediately after electroplating at approximately 200 degrees for up to eight hours to get rid of as much hydrogen as possible.
Other elements that can be applied to steel springs by electroplating include gold, silver, tin, and nickel. Tin and nickel are mostly used in situations where good electrical conductivity is necessary.
If you are looking for good finishes for larger springs, invest in powder coating. You can achieve a wide range of colors for decorative purposes, corrosion resistance, or for unique identification. The paint adheres quite lightly to the spring.
However, powder coating isn’t always ideal for smaller springs since the thickness can be substantial. The cost of powder coating can also be a significant disadvantage since the price of a powder coated spring is much higher than that of an uncoated spring.
Mechanical springs can also be coated using a pre-plated wire. This can be achieved by drawing the spring wire through molten metal which also lowers the risk of hydrogen gas embrittlement. Zinc is used as the primary coating material and wires treated in this manner are usually referred to as “galvanized” wires.
The primary advantage of using a pre-plated wire is that it is a low-cost method of coating springs and ensures full coverage of the wire surface. Even the closed ends of the spring are treated. However, you need to keep in mind that the cut ends of the sire aren’t coated, but it isn’t a big issue. The less common coatings include manganese phosphate, colored dye, black oxide, and many others. Make sure that you consult with experts at The Yost Superior Co. to determine the right coating for your springs.