Question

After a long day of laboratory work, you have returned to find that someone has run into your car in the university parking lot! Although leaving no note, they have left evidence in the form of paint residues at the point of impact. By carefully removing and storing some of the evidence, you return to your lab to perform analysis on the paint.

(i) From the damage caused by the collision the impact looks to have been of considerable force and is assumed to have transferred most material from the suspect car. What substances might you expect to find around the impact. Draw a labelled “layer architecture” diagram for car coatings. (Graduate Capabilities - Chemistry knowledge & skills; Inquiry/Research)

(ii) For the following car coatings, state a general chemical composition, how it is applied, and what damage it acts to protect against; (a) wax, (b) clear-coat, (c) galvanised steel. (Graduate Capabilities - Chemistry knowledge & skills; Critical Thinking)

(iii) Cars often have “metallic paint” to produce a shimmering appearance. What is metallic paint and, with reference to the interaction of light with metal compounds, why do these paints shine? (Graduate Capabilities - Chemistry knowledge & skills; Inquiry/Research)

Answer 1

i) The answer is in the form of image.

ii) Wax: It is the most common form of water repellant which is used to protect plastic materials from being always wet. The coating of wax will keep the car parts free of water, thus will decrease corrosion and increase total life.

Clear coat: It gives shinny uniform metallic paint luster to the car paint. It also protects the car paint from fading away since it blocks UV radiations to reach car paint. It usually in the form of sprays.

Galvanised steel: In most the cases, galvanised steel is used in those areas which are prone to scratched and are more likely to get corroded. It is a transparent and glossy protective coating.

iii) Metallic paints are the mixture of a binder also known as resin, extender that increases adhesive power with the surface, and a basic solvent that will help in drying of any paint. Sometimes, additives are added that can impart additional luster, life and color to the painted surface.

Cars paints shine because of glossy surface. This glossy surface is provided by certain fine materials like Titanium oxide or Calcium carbonate. These materials have very high refractive index due to which the paints shine.