Automotive Coatings

Automotive is the most specification-driven coating market Arctic serves. A component coating is not judged against a general-purpose standard but against a test protocol written by the vehicle manufacturer, and every manufacturer runs its own. The same grade can pass one protocol and fail another on a single clause, so the Arcmotive range is developed against the customer document from the outset: the substrate as moulded, the test list, the exposure hours, the chemical set and the colour tolerance. This is OEM component work, coatings for parts supplied into an assembly line, and it is separate from vehicle bodyshell painting and from bodyshop refinish.

Components are tested for adhesion after humidity and after thermal cycling, for resistance to sun cream, insect repellent, fuel, screen wash and interior cleaners, and for colour stability over years of ultraviolet exposure. The Arcmotive range works on the substrates the industry actually uses: ABS, PC/ABS, ASA, polyamide and polypropylene, primed and unprimed, together with cast and forged aluminium for wheels. Substrate behaviour governs the specification as much as the coating does. Polypropylene has a low surface energy and will not hold a coating as moulded, so it needs flame treatment, atmospheric plasma or a chlorinated polyolefin adhesion promoter before the first coat. Flame and plasma treatment has to be measured and time-limited, because the effect decays in storage, and an adhesion promoter is a coating in its own right with its own film build and recoat window. Polyamide and glass-filled grades carry moisture and release agent that must be dealt with before coating. Polycarbonate lenses are optically clear and soft, so the coating carries the abrasion duty for the life of the lamp.

The range is organised by the part, because the failure mode follows the part. Interior trim and consoles are governed by contact wear, hand cream and cleaning chemistry. Exterior trim and mirror housings are governed by weathering, thermal cycling and the colour match to an adjacent painted panel. Lighting divides into hardcoats for polycarbonate lenses, where haze after abrasion is the controlling number, and the vacuum metallising base and top coat pair for reflectors, where the base coat must level a moulded surface to an optical finish and the top coat must protect a metallised film only tens of nanometres thick. Wheels turn on stone chip at the face and on filiform corrosion creeping from a scribe or a stone strike at the rim flange. Under-bonnet parts turn on continuous heat and on contact with oil, coolant and brake fluid.

Arctic supplies these grades from a technical centre and laboratory in Greater Noida and a production line built for batch-to-batch consistency, which matters here because an approved automotive colour and gloss is locked to a master panel and every subsequent batch is judged against it. Colour matching, gloss level, texture and effect pigment orientation are set during development and then held. A compliance dossier, a technical data sheet, a safety data sheet and a declaration covering the substances your specification restricts are issued on request for each grade.

Matt, satin, gloss and soft-feel finishes for instrument panels, bezels, consoles, armrests and switchgear on ABS, PC/ABS and polyamide. Selection is driven by touch, by resistance to sun cream, insect repellent and interior cleaners, and by abrasion at high-contact points.

Weather-durable basecoat and clearcoat systems for mirror housings, grilles, pillar covers, spoilers and body-side trim on ASA, PC/ABS and treated polypropylene. Selection is driven by xenon arc exposure hours, by colour and gloss retention against an adjacent painted panel, and by adhesion after thermal cycling.

Abrasion-resistant hardcoats for polycarbonate headlamp and tail-lamp lenses, and the coatings that sit either side of a reflector metallising step. Selection is driven by haze after Taber abrasion, by yellowing under ultraviolet exposure, and by the cure method available on the line.

Primer, basecoat and clearcoat for cast and forged aluminium wheels, wheel covers and hub caps. Selection is driven by multi-impact stone chip rating at the face, by filiform corrosion resistance at the rim flange and bead seat, and by resistance to brake dust and wheel cleaner.

Coatings for engine-bay brackets, covers, housings and fasteners that see continuous elevated temperature together with splash contact from oil, coolant, fuel and brake fluid. Selection is driven by the continuous service temperature, by the oven temperature the part will take, and by the fluid list in the protocol.

The base coat and protective top coat pair used around aluminium vacuum metallising on reflectors, bezels and decorative trim. The base coat levels the moulded surface to an optical finish and the top coat protects and tunes the appearance of the deposited metal layer.

The figures below are the typical operating window for this range, not a measured result for any one batch. Confirmed values are issued with the Technical Data Sheet and Certificate of Analysis by our laboratory.

Substrate preparation decides the result

Every Arcmotive grade is applied to a surface that has to be right before the gun opens. Mouldings arrive with residual release agent, plasticiser bloom, static-held dust and, on polyamide and glass-filled grades, absorbed moisture. Parts are degreased or washed, dried, and where the specification calls for it destaticised with ionised air immediately before coating. Aluminium wheels are degreased, etched and given a chromate-free conversion coating, and the pretreatment bath concentration and rinse quality govern filiform corrosion at the rim far more than the clearcoat does.

Polypropylene is the case that catches lines out. As moulded it has a surface energy too low to wet out, so it needs flame treatment, atmospheric plasma or a chlorinated polyolefin adhesion promoter. Flame and plasma treatment is measured, not assumed, and it decays: wetting tension is checked with dyne solutions on the principle of ASTM D2578, and the part is coated inside an agreed hold time, typically minutes to a few hours depending on the grade of polypropylene and the store conditions. A treated part left overnight is an untreated part. An adhesion promoter behaves differently, because it is a coating rather than a surface treatment, so it is controlled by film build and by its own recoat window instead of by a wetting tension check.

Application and cure

Pigmented and clear grades are spray applied, by robot bell or reciprocator on volume lines and by hand gun for low volume and repair. Electrostatic application is used on aluminium wheels, and on plastics only where a conductive primer or a conductive moulding provides the earth path, for transfer efficiency and edge coverage. Hardcoats and metallising base coats are more often flow coated or dipped, because a flowed film follows lens curvature and reflector geometry without the shadowing a spray gun produces. Two-component grades are mixed at the stated ratio, given the stated induction time and used inside pot life, with mixed material never returned to the pot.

Cure is the second half of the specification. Stoving and two-component grades need the stated metal or part temperature held for the stated time, measured with an oven profiling data logger travelling with the part rather than read from the oven setpoint, because a heavy aluminium wheel and a thin-wall bezel reach temperature at different rates. Ultraviolet grades need the stated dose in millijoules per square centimetre at the part surface, measured with a radiometer on the conveyor, and lamp output falls with hours in service. Undercure shows up first as a chemical spot failure and as adhesion loss after humidity, not as a visible defect on the line.

Line conditions

Booth temperature, humidity and air cleanliness are part of the specification. Exterior and metallising work is done under filtered air with controlled temperature and relative humidity, because a dirt inclusion in a reflector base coat becomes a visible defect once the part is metallised. Viscosity is set at the gun with a flow cup at a stated temperature, not by eye. Racking and jigging are fixed during development, since the jig marks, the earth contact on electrostatic work and the part orientation during flash off all affect where sags, dry spray and uncoated edges appear. On the metallising line the hold time between base coat cure, metallising and top coat is controlled, because a bare aluminium layer begins to oxidise as soon as it leaves the chamber.

Quality control on the line

Colour and gloss are read against the approved master panel on every batch and at a set frequency through the shift, to ISO 2813 at 60 degrees for gloss and with a spectrophotometer for colour. Film build is checked wet and dry, and adhesion is checked on a witness panel run with the parts rather than on the parts themselves. Each Arcmotive batch ships with a certificate of analysis, and retained samples are held so that a field question can be traced back to the batch that made the part.

Automotive component coatings cannot be specified from a colour and a finish alone. The answers below are what Arctic needs in order to put a grade forward, and the more of the customer protocol you can share at the enquiry stage, the fewer development loops the programme takes.

The part and the substrate

• What is the part, and is it interior, exterior, lighting, wheel or under-bonnet?
• What is the substrate, by polymer grade and filler content, and who moulds it? ABS, PC/ABS, ASA, polyamide, polypropylene, polycarbonate and aluminium each change the answer.
• Is the part primed, unprimed, or moulded in colour? If polypropylene, is flame, plasma or adhesion promoter available on the line, and what hold time can you guarantee between treatment and coating?
• What release agent is used in the tool, and can the part be washed before coating?

The specification

• Which customer protocol governs this part, and can you share the document or the test list? This is the single most useful item in the enquiry.
• What are the required exposure hours for accelerated weathering, and which apparatus and cycle?
• What is the chemical resistance list, with contact time and temperature for each reagent?
• What thermal cycling range and how many cycles? What is the maximum continuous service temperature for under-bonnet parts?
• For wheels, what stone chip rating, what salt spray hours and what filiform corrosion limit, and at which locations on the rim?
• For lenses, what is the haze limit after Taber abrasion, at how many cycles and under what load?

The appearance

• What colour, and is there a master panel, a physical standard or a painted panel the part must match?
• What gloss level at 60 degrees, and what tolerance? Is the part matt, satin, gloss, soft-feel, metallic or metallised?
• Does the part sit next to a painted metal panel, and must it match under more than one light source?
• What is the acceptable colour and gloss shift after weathering?

The line

• Is application by robot bell, reciprocator, hand spray, flow coat or dip, and is electrostatic application available? If it is, does the part carry a conductive primer or a conductive moulding?
• What oven capacity, dwell time and metal or part temperature can you reach, and what is the maximum temperature the moulding will take without distortion?
• For ultraviolet cure, what lamp type, conveyor speed and measured dose at the part surface?
• For metallised parts, what hold time can you hold between base coat cure, metallising and top coat?
• What is the required line rate, the batch size and the annual volume?
• Are there volatile organic compound limits at the site, and is a waterborne or higher-solids route needed?

Documentation

• Which substance restrictions apply to this programme, and what declarations does your customer require with the part?
• What sampling, retained-sample and certificate-of-analysis arrangement do you need for production release?

Send the protocol, the substrate and moulded plaques or actual parts, and Arctic will coat and test to your list before a grade is proposed.

The Technical Data Sheet, Safety Data Sheet and regulatory declaration for any grade in this range are issued by our laboratory against the substrate and process you are running. Tell us the job and we will specify against it.