Depending upon the requirement for industrial fasteners, there are several types of fastener coatings available today. In this article, we’ll cover few major important fastener coatings and finishes in detail that are widely used in several industries across the globe in today’s era.
Mechanical Galvanizing
In this process, the fasteners are placed in a big rotary barrel. Other components such as zinc powder, special promoters, and glass impact beads are also added to the barrel. As a result of the rotation of the barrel, the mechanical energy generated gets transmitted through the glass impact medium which blasts the surface of the fasteners with zinc particles. Because of this, the zinc powder is mechanically welded on the surface of the fasteners. The process of mechanical galvanizing is conducted at room temperature.
Since zinc is more reactive as compared to iron, the zinc coating corrodes first (sacrifices), thereby protecting the steel substrate. As a result of this, a thick zinc coating is said to provide cathodic protection, also known as sacrificial protection to steel fasteners. The rate at which zinc corrodes is about ten times slower as compared to that of steel, hence a thin zinc coating can protect steel for a long duration.
The process of mechanical galvanizing is a preferred process for structural applications as it gives result to a uniform coating thickness. This decreases issues pertaining to thread fit during assembly. Additionally, the process is also consistent over batches. Mechanical galvanizing can be used for a wide range of structural products such as ASTM A325, A563 Grade DH construction bolts, heavy-duty hex nuts, A307 bolts and studs, A449 hex bolts, F1852 tension control assemblies and F436 hardened steel washers, DIN 6914, DIN 6915, DIN 6916 and for bolts with small diameter, as well as fine-thread screws etc. Few applications for mechanical galvanizing include the following:
- Increases lifespan of the fasteners
- Make utensils rust free
- Utilized in majority of the commercial construction projects
- Industrial applications for improving lifespan of metal pipes and the wires
Electroplating
This process is widely used for fastener coatings and is preferred by many industries globally. In electroplating, the surface of the fastener is first cleaned carefully in an alkaline detergent-like solution. Post this step, it is treated with acid so as to get rid of rust or surface scales, if any. The process of properly cleaning the fastener before proceeding further is extremely crucial since the molecular layers of oil or rust on the fastener surface can prevent the adhesion of the desired coating to the surface of the metal.
To achieve electroplating, the process of electro-deposition is applied. In this, the fasteners are immersed in a chemical bath comprising of dissolved zinc. On applying direct current, the zinc at the anode starts dissolving, and the free metal ions reach the cathode forming a thin coating layer on the fastener. The resulting thickness of zinc coating will depend on several factors such as the chemical composition of the plating bath, the time spent in the plating bath, and the amount of electric current applied.
The process of electroplating is an affordable process. Also, since the coating achieved in this process is thin, it does not interfere with the fastener threads. Electroplating has numerous applications in various sectors wherein a metal is coated with another metal to improvise corrosion resistance. A few of the major applications of electroplating involve:
- Reducing friction
- Protection against all surface abrasions
- Increasing wear resistance
- Improving the overall electrical conductivity
- Preparing surfaces for great adhesion prior to painting and re-coating
- Gold and Silver Plating
Polytetrafluoroethylene (PTFE) or Teflon
PTFE coating is a synthetic fluoropolymer of tetrafluoroethylene and has numerous uses globally today. This coating process has applications across various industries as it enables achieving smooth, low-friction, chemical resistant, and corrosion-resistant coating. A temperature range of 290°C is known to keep the polytetrafluoroethylene (PTFE) coating most effective and yields the best results.
The process first involves preparing the required surface for coating. This involves properly cleaning the surface to be coated to achieve the best coating and extend the life of the coated surface. After completion of this step, it is time for the PTFE application. The application of coating can be done in a number of ways, of which spraying and electrostatic coating are known to be among the most preferred ones.
On successful completion of PTFE coating application, they are usually oven-baked to dry and cure as the final step. It is during this step that the desired thickness of the coating, as per the application requirements, is successfully achieved.
Few applications for PTFE or Teflon in our lives involve the following:
- Majorly utilized in electrical appliances
- Prevents food from sticking the cookware products
- Used widely in semiconductors
- Chemical, Automobile and the Food Industry
- Construction, Medical and the Energy Sectors
- Fabrics and even in majority of the personal care products
We at Mac-Fit Industries provide India’s largest PTFE coated B7 Studs. In addition to this, we are nut bolt manufacturers, and PTFE coated anchor bolt and anchor fastener exporters with years of hands-on enriched experience in the field.
Now that you’re aware about fastener coatings and their crucial applications, do let us know other major industrial fastener coating methods which you’re aware of and are utilized globally. Also, Mac-Fit Industries is a global fastener manufacturer and supplier since 1982, enhance your knowledge by following us for more similar articles on our social profile and do reach out to us in case of any custom fastener requirements and we’ll be happy to assist you’ll with the same.
