Koch-Chemie PreWash express "Pe" Pre-wash 5kg

Car pre-wash that lifts bugs and road salt touch-free

What is the PreWash express "Pe" from Koch-Chemie? A high-alkaline pre-wash concentrate for detailers and high-throughput car washes. It breaks down baked-on bugs, bird mess and winter road salt chemically in under a minute, before a wash mitt ever touches the paint. Not for anodised trim, bare aluminium or your weekly maintenance wash.

PreWash express "Pe" from Koch-Chemie in Unna is a no-compromise high-alkaline car pre-wash — the first stage of a touch-free wash. The high-strength, phosphate-free concentrate pairs modern complexing agents with special surfactants and lifts organic grime like insect protein, road film and grease through saponification and proteolysis. The alkali splits the bonds inside the dirt, it turns water-soluble and rinses off, instead of grinding across your clear coat under the mitt.

• The dirt drops before the first mitt comes near. "Pe" softens bugs, bird mess and traffic film in a minute flat — far enough that the pressure washer blasts them off. Every grain you flush off touch-free is one that can't drag a scratch through the paint later. That's the whole point of a pre-wash.
• One concentrate, three jobs. Depending on how dirty things are, you mix 1:30 to 1:100 for the paint pre-wash, 1:4 to 1:20 for wheels, and 1:2 to 1:15 for wash-bay floors and walls. A 23 kg drum stretches to around 2,300 litres of ready-to-use solution. The complexing agents grab calcium and metal ions in the water, so even hard tap water won't drag the cleaning power down.
• Phosphate-free, low-foam, easy on the plant. "Pe" is VDA class B — the standard for short contact times in car washes: a minute at most, 1:100 at most. It works with biological grey-water treatment, and the deliberately low foam shortens the rinse. That profile is exactly what express car washes need.

Day-to-day from Detailing1: The most expensive mistake with a high-alkaline pre-wash is laying it down in the sun or on warm paint. The water flashes off in seconds, the concentrate burns into the clear coat as a milky haze — and the only way back out is the polishing machine. Work in the shade, on a surface that's cool to the hand, and run two short passes rather than one long dwell. What we see day-to-day: etch one black bumper like that and you never forget the rule again.

Mix cool, dwell short, rinse hard

Always lay the car pre-wash down diluted, on cool bodywork that hasn't heated up — work bottom to top and rinse it off completely with the pressure washer after a minute at most. That keeps the reaction in the safe zone.

Why pre-wash at all? The coarse grit you pick up on the road — silica dust, bug shells, salt crystals — acts like sandpaper the moment you start washing. A car pre-wash takes those particles apart through proteolysis and saponification: protein and grease lose their grip, the pressure washer carries them off before a sponge or brush ever touches the surface.

How strong you mix depends on the kit. In a pump sprayer — an IK pressure sprayer, say — the mix you make up hits the paint neat, so you deliberately go thinner here and meter it precisely.

With a foam lance it's the other way round: the pressure washer's water stream dilutes the bottle mix hard a second time, about tenfold. If you want a clean 1:100 on the paint through the lance, you mix the bottle at around 1:10 to start with. All that counts is what actually lands on the paint — plenty of people get that sum wrong and lay it down far too strong by accident.

The three dilution windows aren't arbitrary, they're working ranges: 1:30 to 1:100 for the paint pre-wash on a car, 1:4 to 1:20 for loose wheel grime and brake dust on alkali-resistant wheels, 1:2 to 1:15 for algae, oil film and biofilm on bay floors. The more delicate the surface, the thinner the mix and the closer your eye on the clock.

Bottom to top stops run-off concentrate streaking on dry panels. With heavy build-up — crusted bugs after a motorway run, a thick layer of salt in February — a second short pass beats leaving it to sit. Letting it dry is off the table: a dried alkaline film is exactly what leaves the marks afterwards.

Anodised and bare aluminium stay off-limits

"Pe" is cleared for intact clear coat, steel wheels and alkali-resistant painted alloy wheels — not for anodised aluminium, bare metal or mirror-polished rims. That line isn't red tape, it's chemistry.

Anodising is the satin, electrochemically sealed protective layer on a lot of trim strips, window frames and roof rails on premium cars. Aluminium is amphoteric — it dissolves in strong alkalis just as it does in acids. Let "Pe" hit a strip like that too strong or too long and the alkali eats into the layer, leaving milky-white, iridescent marks. They won't polish out; the strip has to be replaced. On bare or polished alloy the metal reacts on contact and dulls right off.

On intact clear coat, though, "Pe" is safe as long as you hold the minute. Modern clear coats are highly cross-linked polymers that shrug off a short alkaline spike with no trouble; dilute to 1:100 and the working pH on the paint drops into the 11 to 12 region anyway. Steel wheels and powder-coated, alkali-resistant alloy wheels take the stronger wheel dose — all that matters is the wheel isn't bare, anodised or mirror-polished.

The second hard line is heat. On a sun-warm bonnet the water in the solution flashes off in seconds, the alkali concentrates back up in spots and etches the clear coat. What's left is baked-in tide marks that only a machine polish removes. So the rule stands: never in full sun, never on hot metal.

And "Pe" doesn't tell the difference between dirt and a protective layer. A product around pH 13 is as caustic as a drain cleaner and strips waxes, sealants and weaker coatings clean off. That's exactly why it's not a maintenance product. If you want to wash your waxed or ceramic-coated car gently, stick to the pH-neutral car shampoo; "Pe" would take the protection off along with the dirt.

Built for high-throughput washing, not the weekend

"Pe" earns its keep where speed matters: in express car washes, on fleets, commercial vehicles and badly soiled cars — not on a relaxed weekend wash in the driveway.

In the wash tunnel that short, no-compromise action is an upside: the plant meters precisely, cycles fast and rinses through quickly thanks to the low foam. For the detailer working by hand, that's the catch. The VDA minute is gone fast once you've walked a big SUV with the pump sprayer — by the time you're back, the concentrate at your starting point has been sitting far too long. So you work "Pe" in sections: spray one side, rinse, then the next.

Detailers reach for "Pe" as a dirt-breaker on purpose, not as an all-rounder: for neglected used cars, winter salt crust, engine bays, or to strip wax before a polish and re-seal. Within the Koch-Chemie line-up it's the top energy stage. If you want the classic, higher-foaming pre-wash for longer dwell times, the sister product Vorreiniger B is the better fit; "Pe" is the low-foam, express-tuned option in the Pre-wash range.

The numbers stack up mostly in volume work. A 23 kg drum makes around 2,300 litres of finished pre-wash solution at 1:100 — enough for hundreds of cars. Spread across a single wash the product cost barely shows; the real lever is the time the short dwell phase saves per car. For a handful of cars a month the 5 kg pack lasts a long while instead, with no concentrate ageing unused.

The pack sizes follow that logic: 5 kg to get started and for smaller operations, 23 kg as the standard drum for a running plant, 225 kg in the barrel for high-frequency wash tunnels with automatic dosing. The one thing no label spells out: the maximum dwell time isn't a suggestion, it's the safety limit. "Pe" is built for the machine that's done in 60 seconds. Respect that by hand and work in sections, and you get the full dirt-cutting power without ever risking a trim strip.

Application of Koch-Chemie PreWash express Pwe

Preparation and starting cold

Drive the vehicle into the shade or a cool place and cool down the bodywork with cold water. Pwe cannot tolerate components above 25 degrees Celsius or direct sunlight – the lye concentrates when drying and etches visible streaks into the clear coat.

Safety goggles, chemical-resistant gloves, and closed work clothing are mandatory when handling the concentrate. Pwe is highly alkaline and reacts immediately with skin and eyes.

Mixing and application

Mix concentrate using a foam lance or pressure sprayer. For bodywork, 1 part concentrate to 50 to 100 parts water; for heavily soiled steel or alkaline-resistant painted aluminum rims, 1:4 to 1:20; for car wash bay floors, 1:2 to 1:15. In an express car wash, the dosage at the entrance is typically 1 to 2 percent.

Always spray Pwe from bottom to top – from the sills over the doors and fenders to the front, then to the hood, and finally to the roof. This ensures the lower area remains in contact with the lye for the longest time, and the cleaner does not run from the top into untreated areas.

One minute, then high-pressure

Allow to dwell for a maximum of 60 seconds – start a stopwatch from the first second. Rinse with a high-pressure cleaner and a 25-degree flat jet nozzle at a minimum of 100 bar, at a distance of 30 centimeters, again from bottom to top. The jet removes 80 to 90 percent of the loosened dirt without contact.

On sunny days, immediately after applying Pwe, cover with a layer of pH-neutral Gentle Snow Foam Gsf – the dense foam carpet keeps the lye moist and prevents it from drying out.

This must be followed by a manual main wash with pH-neutral car shampoo using the two-bucket method. Pwe does not replace the main wash; it prepares for it.

Notes: Pwe is not suitable for regular wax maintenance washes – the lye strips carnauba waxes and simple polymer sealants. Also taboo are raw or anodized aluminum, natural leather, convertible tops, unprotected polycarbonate headlights, and all interior components. Inorganic lime and baked-on industrial fallout are beyond its reach – for these, acidic cleaners are needed. Store frost-free between 5 and 30 degrees Celsius, in original packaging, tightly closed, separate from food and animal feed.