Every cleaner sits somewhere on the pH scale, and where it sits decides what it cleans well and what it can damage. This guide explains pH in plain terms, then shows surface by surface what is safe to use on cars, motorbikes and bicycles.
The short version: stay close to neutral for routine washing. Move towards alkaline for oily dirt and towards acid for brake dust and mineral deposits, but only on surfaces that can take it, only for a few minutes, and never let it dry.
What pH means
pH is a scale from 0 to 14 that measures how acidic or alkaline a water based liquid is. 7 is neutral. Below 7 is acidic. Above 7 is alkaline.
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- Each step is ten times stronger. pH 12 is ten times more alkaline than pH 11 and a hundred times more than pH 10. The gap between a pH 10 snow foam and a pH 13 traffic film remover is far bigger than it looks.
- Acids dissolve minerals and metal. That is why they shift brake dust, rust, limescale and water spots, and why they also attack bare metal.
- Alkalis break down oil and grease. That is why they shift traffic film, bugs and chain grime, and why they also strip wax and attack aluminium.
- Diluting helps less than you think. Diluting a cleaner ten times moves it one step closer to neutral at most. A strong cleaner is still strong at the ratio on the label.
Where cleaners sit on the scale
| pH | Band | Typical products | For comparison | Good at |
|---|---|---|---|---|
| 0 to 2 | Strong acid | Heavy duty acid wheel cleaners, brick and concrete cleaners | Battery acid, about 1 | Baked on brake dust, rust and cement. High risk on almost every finish. |
| 3 to 5 | Mild acid | Water spot removers, limescale removers, some wheel cleaners | Vinegar, about 3. Bird droppings, about 3 to 4.5 | Water spots, mineral deposits and light brake dust. |
| 6 to 8 | Neutral | pH neutral shampoo, neutral snow foam and wheel cleaner, many iron fallout removers | Pure water, 7 | Loose dirt on a vehicle that is washed often. Kind to wax, sealant and coatings. |
| 9 to 11 | Mild alkaline | Most snow foams and pre washes, all purpose cleaners, bike washes | Bar soap, about 9 to 10 | Traffic film, bugs and light grease. |
| 12 to 14 | Strong alkaline | Caustic traffic film removers, engine degreasers | Oven cleaner, about 13 | Heavy grease and baked on oil. High risk on aluminium, trim and protection. |
These are typical ranges, not a rule for every brand. The pH of any product is on its safety data sheet, usually in section 9.
How acids and alkalis cause damage
Acids (low pH)
- Etch bare and polished aluminium, leaving a dull white or grey bloom.
- Get under chipped lacquer on diamond cut wheels and start the white worm corrosion that spreads beneath it.
- Strip the zinc plating from bolts and brackets, which then rust.
- Flash rust bare steel such as brake discs, chains and spokes.
- Etch clear coat when left to dry in the sun. Bird droppings do exactly this.
Alkalis (high pH)
- Strip wax and sealant. That is useful before polishing and a problem the rest of the time.
- Attack aluminium and fade or strip anodising. Aluminium is damaged at both ends of the scale.
- Leave white stains on black plastic trim and dry out rubber when they dry on.
- Cloud and craze polycarbonate such as headlight lenses, motorbike screens and visors.
- Streak matt paint and wraps, which cannot be polished to put it right.
- Dry out and stiffen leather, which is naturally slightly acidic.
The matrix: surface by pH
Find the surface on the left, then read across to the pH band of the product you want to use. The ratings assume the product is at its label strength, on a cool surface, for a few minutes, followed by a thorough rinse.
- Safe Fine in normal use. Rinse it off and do not let it dry.
- Care Short contact only, at the right dilution. Test a hidden area first. Regular use will cause wear.
- Avoid Likely to mark or damage the surface. Use something else.
Swipe the table sideways to see every band.
| Surface | Strong acid pH 0 to 2 |
Mild acid pH 3 to 5 |
Neutral pH 6 to 8 |
Mild alkaline pH 9 to 11 |
Strong alkaline pH 12 to 14 |
|---|---|---|---|---|---|
| Paint and finishes | |||||
| Clear coated paint Most modern cars, motorbike panels and bicycle frames |
Care Rinse fast. Etches if left |
Safe | Safe | Safe |
Care Dulls if it dries on |
| Single stage and classic paint Older cars and bikes, some solid colours |
Avoid Stains and etches |
Care Short contact |
Safe |
Care Can dry it out |
Avoid Dulls and stains |
| Matt and satin paint Cars, motorbike tanks, helmets and frames |
Avoid Marks cannot be polished out |
Care Short contact |
Safe |
Care Can streak |
Avoid Leaves shiny or pale patches |
| Vinyl wrap and paint protection film Cars, motorbikes and frame protection |
Avoid Can stain the film |
Care Check the film maker |
Safe |
Care Check the film maker |
Avoid Can stain and lift edges |
| Wax and spray sealant Any painted surface |
Care Shortens its life |
Safe | Safe |
Care Shortens its life |
Avoid Strips it |
| Ceramic coating Paint and wheels |
Care Occasional use only |
Safe | Safe |
Care Check the coating maker |
Care Wears it with repeated use |
| Wheels and metal | |||||
| Painted, powder coated or lacquered alloy Most car and motorbike wheels |
Care Sound finish only |
Safe | Safe | Safe |
Care Stains if it dries on |
| Diamond cut alloy Car wheels with a bright machined face |
Avoid Gets under chipped lacquer |
Care Sound lacquer only |
Safe |
Care Sound lacquer only |
Avoid Gets under chipped lacquer |
| Bare or polished aluminium Polished rims, engine cases, fork legs, bicycle rims and cranks |
Avoid Etches. White bloom |
Care Rinse promptly |
Safe |
Care Can darken it |
Avoid Etches and blackens |
| Anodised aluminium Bicycle parts, levers, trim and roof rails |
Avoid Strips the anodising |
Care Rinse promptly |
Safe |
Care Rinse promptly |
Avoid Fades and strips it |
| Chrome plating Exhausts, trim, handlebars and classic bumpers |
Care Pits worn or thin chrome |
Safe | Safe | Safe |
Care Rinse promptly |
| Magnesium Some motorbike and race wheels, engine covers |
Avoid Corrodes fast |
Avoid Corrodes |
Safe Dry it after |
Safe |
Care Rinse promptly |
| Zinc plated and galvanised steel Bolts, brackets and brake fittings |
Avoid Strips the plating |
Care Thins the plating |
Safe | Safe |
Care Thins the plating |
| Bare steel and cast iron Brake discs, sprockets, cassettes and spokes |
Avoid Rusts fast |
Care Flash rust |
Safe Dry it after |
Safe Dry it after |
Care Strips protective oil |
| Stainless steel and titanium Exhausts and fasteners |
Care Can dull or strip heat colour |
Safe | Safe | Safe | Safe |
| Plastic, rubber and glass | |||||
| Unpainted black plastic trim Bumpers, arch trims, mudguards and scuttle panels |
Care Can fade it |
Safe | Safe | Safe |
Care White stains if it dries on |
| Rubber and tyres Tyres, door seals, hoses and fork gaiters |
Care Rinse promptly |
Safe | Safe | Safe |
Care Dries rubber out |
| Glass Windscreens, windows and mirrors |
Care Some acid cleaners etch glass |
Safe | Safe | Safe |
Care Can haze if left |
| Polycarbonate Headlight lenses, motorbike screens and visors |
Care Rinse promptly |
Safe | Safe |
Care No ammonia |
Avoid Clouds and crazes |
| Carbon fibre Bicycle frames and wheels, motorbike and car trim |
Care Rinse promptly |
Safe | Safe | Safe |
Care Can dull the lacquer |
| Drivetrain and seats | |||||
| Chains Bicycle chains, O ring and X ring motorbike chains |
Avoid Rust and weakened links |
Avoid Rust and weakened links |
Safe Dry and re lube |
Care Rinse, dry and re lube |
Avoid Can weaken links and seals |
| Leather and Alcantara Car interiors, motorbike seats and saddles |
Avoid Burns and stiffens |
Care Test first |
Safe |
Care Dries leather out |
Avoid Strips colour and oils |
This is a general guide. Finishes vary and so do products. If the maker of your vehicle, wrap, coating or component says something different, follow them. Wrap makers are a good example: Avery Dennison asks for cleaners between pH 5 and 9, and 3M advises against strongly acidic or alkaline cleaners on its protection film.
What the matrix cannot show
- Time and heat. A hot wheel or a panel in the sun speeds up every reaction, and a cleaner gets stronger as it dries. The same product can be safe for two minutes in the shade and leave a mark after ten in the sun.
- Condition. Chipped lacquer, worn chrome and faded paint have already lost their protection. Drop one rating for anything tired or damaged.
- Solvents. Tar removers and some degreasers are solvents, so pH does not apply to them. They can soften fresh paint, some plastics and rubber, and they remove wax.
- Salt. Road salt is close to neutral. It corrodes metal through chloride, not through pH, so it needs rinsing away whatever cleaner you use.
- Mixing. Never mix products. An acid and an alkali cancel each other out and can give off heat or fumes.
By vehicle
| Vehicle | Most sensitive parts | Keep to | Watch for |
|---|---|---|---|
| Car | Diamond cut and polished wheels, matt paint, wraps, black trim, wax and sealant | Neutral for routine washes. Mild alkaline when it is properly dirty. Acid only on sound painted or lacquered wheels. | Wheel cleaner drying on paint, calipers and wheel nuts. |
| Motorbike | Bare aluminium engine cases and fork legs, anodised parts, zinc plated fasteners, O ring and X ring chains, screens and visors | Neutral to mild alkaline, well rinsed. Nothing strong near the engine, chain or controls. | Cleaner trapped around fasteners and switchgear. Hot engines and exhausts. |
| Bicycle | Anodised parts, chains and cassettes, carbon, disc rotors and pads, suspension seals and bearings | Neutral to mild alkaline bike wash. Degreaser on the drivetrain only. | Degreaser reaching rotors and pads. A chain left dry after cleaning. |
Cars
- Know your wheels before you choose a wheel cleaner. Painted and lacquered alloys take most products. Diamond cut, polished and anodised wheels need a neutral or delicate one.
- Wash wheels first and rinse each one before moving on, so nothing dries on the wheel or the paint next to it.
- On matt paint and wraps, treat every mark as permanent. There is no polishing it out afterwards.
Motorbikes
- A motorcycle has far more bare metal on show than a car. Engine cases, fork legs, hubs and fasteners are often bare or polished aluminium or zinc plated steel, and both react to strong acids and strong alkalis.
- Let the engine and exhaust cool fully before any cleaner goes on.
- Clean screens and visors with an ammonia free cleaner and a soft cloth only.
Bicycles
- Shimano tells riders to clean chains with a neutral detergent and never to use acid or alkali based solvents such as rust cleaners, because the chain could break.
- Anodised finishes on derailleurs, cranks and rims fade with strong cleaners and cannot be touched up.
- Keep every cleaner and degreaser away from disc rotors and pads, and re lubricate the chain as soon as it is dry.
Spotting damage and what can be fixed
| What you see | Likely cause | Can it be fixed? |
|---|---|---|
| Dull white or grey bloom on bare aluminium | Acid or strong alkali left on too long | Usually. Bare alloy can be polished back with a metal polish. |
| Faded, blotchy or streaked anodising | Strong acid or alkali | No. The part needs stripping and anodising again. |
| White worm lines under wheel lacquer | Salt, water or acid getting under chipped lacquer | No. The wheel needs refurbishing. |
| Dull ring or crater in the paint | Bird droppings or a strong cleaner dried on | Light etching polishes out with No.07 Polish and Paint Prep. Deep etching needs a body shop. |
| Water no longer beads | Wax or sealant stripped by an alkaline cleaner | Yes. Wash, dry and reapply No.08 Wax and Sealant. |
| White or grey stains on black trim | Strong alkali dried on | Sometimes. Wash again with a neutral cleaner. A trim restorer can hide what is left. |
| Orange film on brake discs | Flash rust after washing | Yes. It is normal and clears in the first few stops. |
| Rust on bolt heads and brackets | Zinc plating stripped by acid | The plating does not come back. Treat the rust and protect it, or replace the fastener. |
| Cloudy or cracked headlight, screen or visor | Strong alkali, ammonia or solvent | Light haze on a headlight can be polished. Crazing cannot. Replace a damaged visor. |
| Shiny or pale patches on matt paint or a wrap | Strong cleaner, polish or hard rubbing | No. The panel needs repainting or wrapping again. |
Six rules that matter as much as pH
- Start mild. Use the gentlest product that does the job and only step up if it does not.
- Follow the dilution. Mixing stronger than the label makes a product harsher than its pH suggests. Our dilution ratio calculator does the sums.
- Work cool and in the shade. Wheels, brakes, engines and panels should all be cool to the touch.
- Never let it dry. Keep to the dwell time on the label and rinse sooner in sun or wind.
- Rinse thoroughly. Flush behind spokes, around fasteners and along panel gaps, where cleaner hides.
- Test first. Try a small hidden area on any finish you are unsure about.
Where the SoapX formulas fit
The letter after the product number tells you which formula you have. As a rule, Delicate is the gentlest and Extreme is the strongest. The full list is in our formula guide.
| Formula | Strength | Use it on | Think twice on |
|---|---|---|---|
| D, Delicate | Gentlest | Matt paint, wraps, ceramic coatings, anodised and polished parts, carbon | Heavy soiling. It may need a second pass. |
| S, Summer | Everyday | Routine washes on sound finishes | Months of baked on grime |
| W, Winter | Everyday, made for salt season | Road salt, grime and traffic film from October to March | Delicate finishes. Use D on those. |
| X, Extreme | Strongest | Heavy soiling on sound, hard wearing finishes | Matt paint, wraps, bare, polished and anodised aluminium, diamond cut wheels, and any wax you want to keep |
- No.03 Wheel and Rim Cleaner: Summer is pH neutral and safe on all wheel finishes. Delicate is for anodised, polished and painted rims. Extreme is the heavy duty formula for baked on brake dust, and its chemistry is confirmed when testing finishes. Keep Extreme to sound painted and lacquered wheels.
- No.05 Contact Shampoo: Summer is pH neutral and will not strip your wax. Extreme is a deliberate strip wash, so protect the paint again afterwards.
- No.01 Pre Rinse and Bug Remover: Delicate is low alkalinity for coatings, wraps and matt paint.
- No.02 Snow Foam: Delicate is safe on matt wraps and ceramic coatings. Extreme is heavy duty and needs a shorter dwell.
- No.04 Drivetrain and Chain Degreaser: made to cut grease without attacking O ring and X ring seals. Delicate is for carbon and anodised drivetrains.
- No.09 Glass and Visor Cleaner: ammonia free, so it is safe on window tints, screens and helmet visors.
- No.06 Fallout and Tar Remover: Extreme is a solvent tar remover, so pH does not apply. Keep to the time on the label.
Check the label and the safety data sheet for the pH of the formula you have, and see how to use our products for dilutions and dwell times.
Common questions
Is a pH neutral cleaner always the safest choice?
For the surface, almost always. Neutral cleaners are safe on paint, wraps, coatings, anodised parts and bare metal. They are not always strong enough for the dirt. Months of traffic film or baked on brake dust may need a mild alkaline or acid cleaner, used for a short time on a surface that can take it.
Will an alkaline snow foam damage my paint?
Not sound clear coated paint, as long as it is diluted as the label says and rinsed off before it dries. Regular use will shorten the life of wax and some sealants. Choose a gentler foam for matt paint, wraps and anodised trim.
What pH is safe for anodised aluminium?
About pH 5 to 8. Outside that range the anodised layer starts to dissolve. Brief contact with a mild alkaline cleaner that is rinsed off promptly is usually fine, but strong acids and strong alkalis cause fading that cannot be repaired.
Can I use a car wheel cleaner on a motorbike or bicycle?
Only if it is pH neutral. Acid wheel cleaners are made for painted and lacquered car alloys. Motorbikes and bicycles have bare aluminium, anodised parts, zinc plated fasteners and chains close to the wheels, and acid damages all of them.
Does diluting a strong cleaner make it safe?
Safer, not safe. Diluting ten times moves a cleaner about one step closer to neutral at most, so a pH 13 degreaser is still strongly alkaline at any normal ratio. Dilution matters most for how long the product can stay on the surface.
Why do bird droppings damage car paint?
They are acidic, typically around pH 3 to 4.5, and they dry hard in the sun, which concentrates the acid against the clear coat. Soak them off with plenty of water as soon as you can. A layer of wax or sealant buys you time.
Is washing up liquid bad for car paint?
Its pH is mild, so pH is not the main problem. It is made to strip grease, so it takes wax and sealant off with the dirt, and it is not made to lubricate a wash mitt the way a car shampoo is.
Read next
- pH neutral or alkaline snow foam: which should you use?
- How to clean alloy wheels without scratching them
- How to wash a matt paint or wrapped car safely
- Motorbike and bicycle chain cleaning: a simple routine
- Winter car care in the UK: how to deal with road salt
Where the figures come from
- Chains: Shimano dealer manual for chains.
- Vinyl wraps: Avery Dennison cleaning and maintenance bulletin.
- Paint protection film: 3M protection wrap film maintenance guide.
- Anodised aluminium: Metal Finishings Ltd, care for anodised surfaces.
- Zinc plating and galvanising: Galvanizers Association of Australia.
- Polycarbonate: Lexan sheet chemical resistance guide.
Not sure what a finish is or what it can take? Email hello@soapx.co.uk with the vehicle, the finish and the product you want to use, and we will help.
