Platings and Coatings

What is the main purpose for plating and coating hardware?

Hardware is usually coated or plated for corrosion resistance. Corrosion can seriously affect the performance of hardware and so it may need these secondary processes to extend its lifetime. The main difference between the two is that coatings utilize a specific solution and do not change the chemical genetic makeup of the parts.

Types of Platings

The two main types of platings are electro and mechanical. The default, and more economical option of the two, is electroplating. This process occurs when a metal substrate is coated with a sacrificial layer by “electrolytic disposition”. The direct electric current creates a chemical reaction to provide a uniform covering of the metal when the hardware is placed in the electrolyte solution. Electroplating usually has a more appealing finish compared to mechanical plating methods.

Mechanical plating does not require extreme temperatures or electrical charges, instead it relies on a form of cold-welding force and chemical reaction to coat the surface of the part. This means parts do not need to be stripped prior to plating. High grade steel and alloy steel items are suitable candidates for this type of plating. The biggest advantage for mechanical plating is that it “does not produce hydrogen embrittlement and does not require a post-bake cycle.” Hydrogen embrittlement must be prevented because embrittlement can cause reduced ductility and a lessening of load-bearing capacity. This can lead to cracking and brittle failures, when subjected to loads below the anticipated proof or yield strength of the susceptible materials, i.e. strength is significantly decreased.

Types of Coatings 

An advantage of coating as opposed to plating is that this process does not change the chemical composition of the parts. Types of coatings include acrylic, alkyd, epoxy, and zinc-rich. If you have taken an art class in the past, it is likely that you have come across acrylic paint. Acrylic coating can provide a glossy finish. This type of coating is also quick-drying and requires less ingredients which makes the process more convenient. Alkyd coatings are sometimes a good choice for parts that industrial OEMs need. These coatings can be custom formulated to withstand turbulent environments like underwater or underground. In order for this coating to be more effective, heat maybe used to “speed the chemical curing reaction”. This type of coating also takes a longer drying period than some of the other types. Epoxy coatings are usually a mixture of a curing agent with an epoxy polymer. This type of coating is applied in multiple parts where a primer is selected as the base layer and then the epoxy is applied over that based layer. After that, a polyurethane topcoat can be added for aesthetic appeals and enhanced durability. Advantages to epoxy coating include abrasion resistance and strong adhesion to many surfaces. These coatings can also withstand extremely high temperatures, up to hundreds of degrees Fahrenheit, which is higher than most coatings. Like the name suggests, zinc-rich coatings use zinc dusts as corrosion resistant materials to cover the parts. High performance organic zinc is mostly made with “epoxy or polyurethane resin binders”. Advantages of zinc coatings include a “galvanic (electrical current) and a polymeric barrier” and using it with steel can provide a dual layer corrosion protection for the part being coated. Fast-Rite offers the industry leading coatings from Magni, Doerken, and Geomet. 

Talk to a Fast-Rite Expert about your plating and coating requirements!

Resources:

https://magnicoatings.com/products/browse-by-oem/

https://www.doerken-mks.de/en/markets/specifications/

http://www.nofmetalcoatings.com/korea/en/markets-specifications/search.xhtm