Bumper painting and repair is one of the most usual processes at any bodyworkand paintshop as far as plastic repairs are concerned, due in part to where it is on the vehicle’s body and because it is easily exposed to damage.
This part has evolved much over the last few years, both in terms of composition and shape.
In addition to their aesthetics, bumpers have many aerodynamic and, above all, safety functions, it being a critical part absorbing impacts and mechanical pressure at low speed.
Today’s bumpers use a large surface area in the front and rear of vehicles. The part’s size and the type of finish (same colour as bodywork, textured, colour combination, etc.) will influence the painting process to be carried out.
Painting a bumper: possible scenarios
When painting a bumper, as it is a plastic part, you should take into account a series of factors to ensure that it is correctly repaired. The flexibility of the part, its adhesion, mechanical stress or its chemical resistance are factors that will influence its treatment and painting.
To achieve the best possible result, always follow the indications provided for specific processes and products involved in the painting of plastics (plastic putties, adhesion promoters, textured paint, etc.) established by a top-quality paint manufacturer such as SINNEK.
When repairing and painting a bumper, professionals can be faced with different scenarios depending on the severity of the damage. Thus, for larger flaws, the entire bumper can be replaced with a newly manufactured part. In this case, the preparation and repainting process will be different.
Nowadays, the vast majority of vehicle manufacturers supply replacement plastic parts with a pre-intermediate coat treatment (primer).
This way, professionals receive a part that is ready for the finish paint to be applied directly.
On the other hand, it could also happen that the new part lacks this pre-coat of primer, which in turn will influence the painting process. An adhesion promoter or primer that optimises the anchoring of the subsequent coats will have to be applied.
In this tutorial, we will focus on a third possibility. A scenario where the bumper is partially damaged, or insufficiently damaged to require its replacement with a new part. In this case, the steps to be taken are as follows:
Steps to repair and paint a bumper
Prior assessment of damageDeep examination of the extent of the damage for a correct choice of repair process. In the example described, you will not need to use adhesives or weld the plastic. It is surface damage, and therefore does not affect the structure of the part. A good practice is to mark all flaws detected for better controlling the repair.
Identify the type of plasticYou should identify the type of plastic the part is made of, since this will influence its adhesiveness to certain paints. To do this, find the code corresponding to the type of plastic which will be located on the part’s inner side. This is an important step because, if the plastic is compatible with the adhesiveness of the filler to be used (information provided in the filler’s data sheet), it would not be necessary to apply an adhesion promoter beforehand.
Thorough surface cleaningBlow the surface with an air gun, and clean it with soap and water. Then, degrease in depth with a special plastic degreaser to remove any surface substance adhered.
Edge sandingSand the edges of the damage with a P150 or P220 sandpaper and a sanding sponge to prepare the application of plastic putty.
Air gun blowing and cleaningRemove the sanding remains with an air gun, and clean the surface thoroughly again.
Applying adhesion promoter in open areasIf you reach the plastic part during the sanding process, cover the bare areas that show the “live” plastic with a plastic adhesion promoter. This will enhance the putty’s adhesion to the surface of the bumper.
Applying plastic puttyApply a plastic putty, such as SINNEK’s PP/7832. This type of putty provides great filling of cracks and scratches, and excellent sanding and finish smoothness.
Sanding the puttySand the remaining excess plastic putty to level and even the surface. Then, in partial repairs, sand the area to repair, and in large repairs, sand the entire part. To do this, use a refining sandpaper: P320 / P400. In hard-to-reach places and nooks, use a sanding sponge.
Blowing, cleaning and degreasingAfter sanding, clean the surface of the part thoroughly, again using a plastic degreaser.
Applying adhesion promoterCheck whether the type of plastic of the part is compatible with the direct application of the filler (shown in the technical data sheet). If this is not the case, apply an adhesion promoter for fast-drying plastics, such as SINNEK’s PL/1895. If the damaged area is not large, you can use a spray-on promoter to be more productive in the repair. It is advisable not to load too much product to prevent any possible paint detachment or solvent reactions. When applying the product, always follow the specifications provided in the product’s technical data sheet in terms of drying time, gun adjustment, etc.
Applying the primerTo help anchoring the final coat of paint, apply filler to the bumper. Depending on the size of the damage and the type of repair to carry out, you can choose between different filler processes (in all cases the shade of the chosen filler must match the colour shade of the finish).
- Spot Repair: if the surface is not too large, you can use a spray filler, which will help to optimise the repair time, and will provide good filling and adhesion.
- Standard process: use a UHS filler, which will provide good performance in terms of fast drying and easy sanding.
- Wet on wet process: use a wet on wet filler, which will provide a high quality intermediate coat, reducing the repair time as sanding the surface after its application will not be required.
Sanding the fillerOnce the filler has dried, sand the surface with a P400 sandpaper (two-coat systems).
Blowing, cleaning and degreasingOnce again, clean and degrease the whole part thoroughly.
Texture application (optional)If the surface has textured areas that are typical of this type of part, apply a textured paint for bumpers, which will leave a satin finish similar to the original. To achieve this effect, you can use the textured bumper paint PL/7870 by SINNEK.
Applying the finish paintThen, apply the final finish paint. Apply colour and clear coat to the part, always following the specifications of the technical data sheet, and other factors such as the choice of hardener and the room temperature and humidity.
Without a doubt, a correct bumper repair and painting will directly influence the productivity and profitability of the bodywork and paint shop, mainly because this is a very usual type of repair in the day-to-day work of a professional. Take into account the specific characteristics of plastic materials in bodywork, and follow the steps described, and you will be sure to achieve a professional quality finish.