The corrosion protection of a coating is sometimes part of the quality of the paint structure. A distinction is also made here between protection by barrier effect and active protective pigments.
Protection by barrier effect is controlled exclusively by the film thickness (passive corrosion protection). Active corrosion protection involves pigments that „sacrifice“ themselves in a protective manner.
The classic or regular structure for an industrial corrosion protection coating consists of
- a primer or adhesion primer, which can provide active corrosion protection. This includes, for example, the zinc phosphate primer.
- a filler or intermediate layer. Depending on the properties to be used, this must be built up in different ways and may be applied in several coats. This layer makes it possible to build up a substrate-equalizing layer and usually provides corrosion protection by means of a barrier effect (there are also filler systems with active corrosion protection). For certain build-ups or special color tones, this layer can already be colored. This procedure increases the covering power and brilliance in some color shades. In most cases, however, gray tones are used in the base coat (manufacturer-specific recommendations must be observed here).
- and a topcoat layer. These layers usually serve to enhance the look or feel. A further barrier effect is also applied with this layer.
Each manufacturer has its own build-up recommendations for the individual corrosion protection classifications. For this it is imperative to know which influences the coating will be subject to!
In the Refinish – passenger car repair count to the corrosion protecting materials likewise
- the cavity sealing (is only sprayed)
- the seam sealing (can be brushed or sprayed)
- and the underbody protection (brushable or sprayable)
Once again, „Many roads lead to Rome!“
A classic car that is restored from the ground up should look good, withstand the most adverse weather conditions and look good for many years.
In a basic restoration, the chassis is usually blasted to Sa 2 1/2. Here, after extensive cleaning, a 2K epoxy filler can be used to create a very good base. Very expensive restorations even include a KTL coating before the EP filler. This build-up would then be „first-class“.
Restoration should not be carried out „just quickly“ or between door and door. The materials can certainly be adjusted normally too long. The less acceleration the material experiences, the better the final result will be. For this reason, it is advisable to let the epoxy filler stand for one to two weeks. Even better at an ambient temperature of 20°C.
Here, it is also generally important to pay attention to the temperature, since epoxy materials interrupt the chemical drying process at temperatures below 15°C and do not cure to the end!
After the drying phase of the EP filler, you can repair the surface. My thought on this was if I want to have high corrosion protection, why use polyester filler in classic car repair or restoration?!
Here I decided to use EP filler from yachting in these cases. As a result, I have created an overall uniform epoxy substrate and no losses due to hygroscopy as in the polyester filler. Also with the filler, as with the EP filler is the drying time to consider. This one is definitely very sluggish! But what helps a boat in the water can only benefit a car on land.
After finishing the filler work, I put the entire chassis in EP filler again. After all the sanding work to be done for the following paint job, the sealing can begin.
NOTE: The cavity sealant and bitumen-based „non-paintable“ underbody protection are applied only after the paint job. Otherwise, grease or silicones may cause considerable surface disturbances!
I have deliberately omitted a recommendation of grit sizes of the sandpaper or the individual work steps. You will find these in the various instructions.
Before I hear the „whispers“, I try to avoid spray filler by doing good bodywork beforehand.
Note: Some manufacturers have their own build recommendations for these old „darlings“.