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Corrosion Removal

Corrosion Removal
Once all the paint, filler and underseal, glue, etc have been removed using the plastic media blasting process, the corrosion should be visible and can be dealt with. (Sound deadening pads, oil, grease and all the other problem materials must be removed by hand or similar methods).

To remove the surface corrosion an abrasive that is hard enough to scour the surface clean must be used. It needs to be sharp and angular to cut into the corrosion on the surface of the metal but small enough to prevent the heat generation, hammering or peening action that has the potential to damage the panels. This is where a skilled operator is essential to minimise the risk of distortion. 

Because most of the work has already been done using the plastic media, the risk of overworking the surface with the hard abrasive is greatly reduced. There is less need to dwell in one place with the abrasive blast stream, it is this dwell that generates a tiny amount of heat and the stressing action that can cause distortion to panels. The finer the abrasive the less kinetic energy there is in the particle to dissipate when it hits the surface. This makes removal of the surface corrosion slower but leaves a very fine profile on the surface of the steel panel, which is a good key for the paint and any filler required. Using these fine materials is difficult technically because they don’t flow well in the equipment, and they make the operators job more difficult and visibility is a big problem anyway, but we have developed special lighting to help him see into the darkest corners

We then put a zinc phosphate treatment on the surface of the metal. This is an acid based material that is absorbed into the surface of the metal carrying with it a small amount of zinc. It is a metal pre-treatment not a paint, it is clear so hides nothing. It is also a rust converter so there is a chemical reaction that converts any corrosive salts to zinc strontium phosphate, a hard, black and chemically inert material. It effectively eats and solidifies the salts thus stabilising the metal. Without the phosphate there is a real risk of corrosion re-occurring if not protected with paint quickly.

Painting over
The phosphate is a chemical preparation that passivates the surface of the metal, killing corrosive salts and providing a chemical key on to which the paint molecules can lock. This, combined with the profile of the surface, provide a mechanical key that further aids paint adhesion.

The important point is that the product is not solvent based, therefore there is no problem of paint compatibility, you can use whatever paint you like.

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The pictures below give examples of our rust removal work.