The Surface Matters as Much as the Dirt
One of the biggest mistakes we see is choosing a chemical based solely on what needs to be removed.
You also need to ask, “What am I putting this chemical on?”
A cleaner that works well on uncoated concrete may be completely inappropriate for painted metal. A chemical that removes biological growth from one surface may damage another.
Concrete
Concrete is generally more forgiving than many other substrates, but that doesn't mean it's indestructible.
Oil, grease, tire marks, organic growth, and general buildup may require different cleaning approaches.
Be particularly careful with aggressive chemicals and excessive pressure around:
- Older or deteriorated concrete
- Decorative concrete
- Coatings and sealers
- Expansion joints
- Areas where runoff could enter storm drains
And remember that pressure washing can expose weak or deteriorated concrete that was already failing. Don't automatically blame the pressure washer for every surface problem.
Masonry and Brick
Brick, block, and other masonry surfaces require some thought before you start.
High pressure can damage softer masonry, erode mortar joints, and force water into areas where you don't want it.
Chemicals can also create problems if they're incompatible with the masonry or aren't thoroughly rinsed.
In many cases, lower pressure combined with appropriate chemistry is a better approach than trying to blast the contamination off the surface.
Metal
Metal presents a different set of concerns.
Certain chemicals can accelerate corrosion, damage protective coatings, or leave residues behind. If you're cleaning painted or coated metal, you need to consider not only whether the chemical will remove the dirt, but whether it will affect the coating.
And after cleaning, rinsing matters.
Chemical residue left on a metal surface can become a problem long after the pressure washer has been put away.
Roofs and Coated Surfaces
Roof cleaning is another area where the “more pressure = better cleaning” mentality can cause trouble.
Many roof coatings and roofing materials don't respond well to aggressive pressure washing. Depending on the roofing system and the type of contamination, the appropriate approach may involve lower pressure and properly selected chemistry.
But “chemical” doesn't mean “anything goes.”
Always consider the roofing material, existing coating, manufacturer's requirements, surrounding landscaping, runoff, and the potential impact on nearby materials.
If you have questions about which chemicals will work best on certain surface types, our team at Youngstown Spray Equipment can help you make the best choice for your client and your business.
Stay tuned for the last part in this series!