With so many surface prep cleaner options, it can be confusing to know which one is right. But surface prep isn’t just cleaning, it’s a critical step to controlling what your coating has to bond to. The right cleaner depends on what’s on the surface (oil, silicone, rust, dirt) and what you’re applying (paint, primer, powder).
For most automotive and fabrication projects, surface prep will typically come down to one of two types. Depending on the job, this will either be a solvent-based cleaner or a water-based detergent. Here’s how to decide which one is right for each situation.
Alkiline Metal Wash
Choose it for: bare metal cleaning plus corrosion control
An alkaline prep cleaner like Eastwood’s Metal Wash is ideal when you’re dealing with greasy bare steel parts. Much like a laundry detergent, it’s a water-soluble cleaner that leaves the surface ready for coating. This type of cleaner breaks down and rinses away grease, oil, and other contaminants to promote paint or powder adhesion.
This one also includes corrosion inhibitors that can help prevent flash rust for up to about 3 weeks. That’s useful if you can’t you’re your part immediately. A powdered concentrate (7 ounces makes multiple quarts of solution), it’s cost-effective for batches of brackets, suspension parts, and hardware.
Prep Solvent
Choose it for: your “final wipe” before primer or paint
Traditional prep solvents like Eastwood’s PRE are aimed at the contaminants that cause fisheyes and adhesion failure in paint. These might include silicone, wax, polish residue, grease, and dirt. With an easy spray-on/wipe-off process, it flashes off quickly to keep the project moving. Use it on sanded OEM paint, bodywork, fiberglass, or bare metal right before spraying primer or topcoat.
Low-VOC Prep Solvent
Choose it for: working where VOC restrictions matter
If you’re working in an area that restricts higher-VOC cleaners, an alternative like Eastwood Low-VOC PRE offers the same “final wipe” solution. It removes the same silicones, waxes, polishes, grease, and dirt, but it’s formulated to comply with low-VOC requirements. It’s also handy when you want an aerosol option for quick, controlled application on panels and spot repairs.
Low-VOC is also recommended for cleaning bare metal before welding, as it’s a non-chlorinated solvent. Always avoid using chlorinated prep cleaners – especially brake cleaner – when welding. The combination of heat and UV given off in the process can give off toxic gases like phosgene.
Water-Based Solvent
Choose it for: 50-state compliance and powder coating prep
Straddling the line between detergent solutions and solvent prep cleaners are products like Eastwood’s PRE Green. It’s a water-based cleaner that doesn’t require rinsing. Simply wipe the part and allow the surface to dry. PRE Green targets the same problem contaminants (including silicone and wax) while emphasizing no harsh chemicals and broad compliance.
This type of cleaner can be sprayed or wiped on, plus it’s also available in pre-moistened wipes for convenience. In fact, the wipes are perfect for “touch points” (fingerprints, polish residue near trim lines) right before coating.
