Student Engineer  


Finishing Processes

The use of good surface prepping (removal of rust, grease and dirt) and effective primers such as Zinc based will help eliminate any rust coming up through the paint on steels and should help prolong the paintjob in this respect. A good hardwearing top coat is also essential if it is to be used outside to prevent the bare metal surface showing through and becoming susceptible to corrosion.

Plastic Coating:
This is done by again prepping the metal surface then heating up the metal and dipping it into a plastic powder mix ensuring all parts are coated, the second stage commences where by the piece is heated up to a sufficient temperature for the powder coating to melt and form a complete protective seal.

This is a process usually for aluminium alloys, it’s an electrolytic process that causes the natural protective oxidised layer to increase in thickness on the metal parts, Anodising increases corrosion resistance and wear resistance, and provides better adhesion for paint, dyes, primers and glues.
Anodising a metal like aluminium is done by sitting the metal in a bath of acid (usually sulphuric), a current is then passed between the acid and metal, with the metal being the positive electrode (anode) which releases oxygen at the surface of the metal and hydrogen at the negative electrode (cathode). The oxygen released on the surface of the aluminium reacts with it to build a layer of aluminium oxide. The thicker the oxidised coating is required to be the higher voltage must be.

Galvanizing is where by the metal has a zinc coating applied to itself, this is done by either a hot dip coating or electro galvanizing where an electrical current is used to help the zinc adhesion. The zinc acts as a sacrificial metal where by the zinc will usually corrode first offering a timed protection to the coated ferrous metal from water. © 2010