Bitumen sounds super scientific but we typically know them as asphalt. However, other than covering our roads, bitumen is also widely used as a material for waterproofing from thousands of years ago when it was found that traces of bitumen were lined in crop storage baskets in the Indus Valley region, somewhere around present day India and Pakistan. Excessive water has a way of destroying crops, hence the need of waterproofing for the purpose of storing crops.

In the modern day, this destructive capability of water and moisture remains an ever-present threat. In moderate doses, they’re necessary to our lives but when they get into places they don’t belong, they can be destructive, as is the case with corrosion which is why even in the present day, the use bitumen as waterproof coating is still widespread. As is the case with any type of coating, bitumen has to be applied at the recommended thickness level for it to work, hence the need for gauges such as Elcometer 500 for coating inspection.

Bitumen in greater detail

Both the term asphalt and bitumen can be used interchangeably but in practice, the term asphalt usually refers to asphalt concrete, which is a mixture of asphalt (or bitumen) with other construction aggregate. For the purpose of this discussion, the term bitumen will instead be used so as to avoid confusion. Bitumen is a generic term used to describe a category of minerals consisting primarily of hydrogen and carbon with traces of nitrogen, sulfur and oxygen. It is a highly viscous liquid or semi-solid form of petroleum that could be found in natural deposits or as a refined product.

Bitumen is a black, sticky substance with physical characteristics not unlike that of the molasses at room temperature. As is typical with hydrocarbons, bitumen is highly hydrophobic in that they tend to repel or at the very least don’t mix well with water, hence their use as a material in waterproofing. In their various formulation and application, bitumen can be used to waterproof an object by preventing water penetration or to damp proof an object by increasing the object’s resistance to humidity.

Bitumen in waterproof coating

In coating applications, bitumen is used as the foundation for bituminous paints, which are coating products consisting primarily of bitumen that is applied in liquid form. Bituminous paints are made up of bitumen mixed with a solvent, usually mineral spirits or naphtha but can also be mixed with other polymers such as polyurethane or acrylic-based polymers to give the other other characteristics to enhance the performance of the coating. A specialized form of bitumen-based coating is also used in roofing in the form of waterproofing membranes.

What makes bituminous paints highly effective as a sealant or to prevent water ingress is the fact that they’re naturally insoluble in water. This makes them a particularly effective type of barrier coating (coatings that are designed to prevent corrosion by repelling the elements that could cause corrosion which in this case is water) by preventing moisture from making direct contact with the substrate. Bituminous paints also typically have strong adhesion properties with almost any material thereby increasing their versatility.

Other than their hydrophobic qualities, bituminous paints are known to be quite durable and have an innate chemical and UV resistance. When combined with other polymers, bituminous paints can be made more durable and flexible and as a result, they are used as a waterproofing solution in both above and underground applications. No matter the material, iron, steel, aluminum, concrete, plastics, etc, bituminous paints remain a highly viable option to increase resistance against corrosion in the harshest of environments.

The application of bituminous paints

As they come in liquid form, bituminous paints can be applied just as easily as the common house paint. Depending on the shape and size of the surface, you can use typical rollers, brushes or sprayers as you see fit. It should be noted however that bituminous paints do contain solvent so VOC emissions, while not excessive, still exists so the typical safety precautions apply. Don’t apply them in a tight, enclosed space unless you’re wearing a mask.

Surface preparation is also important with bituminous paints. While they naturally have strong adhesive properties, they can be undermined by a dirty surface. When applying bituminous paints over an existing paint, it’s also important to remove any loose or blistering paints beforehand. In an especially harsh environment, bituminous paints can also be applied as a top coat with an additional anti-corrosive layer used as a primer to ensure adequate protection against corrosion.