Fight like with like.
Matching the chemistry to the soil.
Oil comes off because something oily grabs it. Baked carbon does not — it stopped being oil the day it cooked. Rust never was. Three different soils, three different mechanisms, and picking the wrong one is how parts get ruined.
Fight like with like gets you about half the soils that come through a workshop door. This page covers the half it handles, the half it does not, and how to tell which one is on your parts.
There are three ways to get a soil off metal. Dissolve it, change it, or lift the metal ion out of it. Every chemical we supply does one of those three. Place the soil in the right column and the selection is most of the way made.
1 · Oil, grease and cutting fluid
What it is. Chains of carbon and hydrogen with no electrical charge worth speaking of — mineral oil, way lube, straight cutting oil, grease (oil held in a soap thickener), soluble coolant. Chemists call it non-polar. Water is the opposite: strongly polar, every molecule pulling on its neighbours.
Why it stays put. Water will not wet an oily surface. It beads up and runs off, and the oil underneath is never touched. More pressure and more time do not change that, because the water never reaches the soil.
What takes it off. A surfactant. The molecule has a long oily tail that sits comfortably in grease and a water-loving head that stays in the bath. Enough of them line up along the oil surface, tails in, heads out. The film breaks into droplets, each one now carrying a water-friendly outer layer, and the bath washes it away.
Ionic and non-ionic
Both words describe one thing: the electrical charge on the water-loving end of the surfactant molecule. The oily tail that does the lifting is the same either way. Neither word is a grade, and non-ionic is not the premium version.
The charge decides how the surfactant behaves alongside everything else in the bath.
| On the sheet | What it means | What it does in a tank |
|---|---|---|
| Non-ionic | No charge on the head | Low foam, works in hard water, and will sit alongside almost any other chemistry without reacting with it. This is why most ultrasonic detergents lean non-ionic |
| Anionic | Negative charge | Strong on oily soil and loose particulate, and the classic foamer. Hard water knocks it back, because the calcium in the water grabs it before the soil does |
| Cationic | Positive charge | Seldom used as a cleaner. The positive charge makes it stick to metal, which is what a rust inhibitor or a sanitiser is for. A detergent has to let go and leave with the soil |
| Amphoteric | Charge depends on the pH | Mild. Used to soften a harsher blend; seldom the whole formulation |
The second consequence is a mixing rule: do not put an anionic cleaner and a cationic additive in the same bath. Opposite charges find each other, pair off and drop out of solution, and you have paid for two chemicals to cancel each other out. Mixing a rust inhibitor into a degreasing bath is the usual way people discover this.
It says nothing about strength, which metals the product is safe on, what temperature to run, whether it rinses clean, or whether the oil separates afterwards so you can skim it. Those five properties decide the result. Ask for them by name.
What carries it
| Product | Where it sits | Working conditions |
|---|---|---|
| FX Degreaser | Light to medium workshop soils across mixed metals — the general-purpose bath | pH 12 · 5–15% v/v · 45–65 °C |
| AquaVantage 815 QR-NF | Heavy-duty immersion and ultrasonic duty — greases, carbon and tenacious soils on steel, aluminium and titanium | 5–30% v/v · 54–77 °C · not for copper or brass |
| AquaVantage 1696 GD | The gentle end — sensitive substrates and mixed-metal assemblies, including copper alloys | Near-neutral, pH ~8 · 3–15% v/v · 49–82 °C |
| AquaVantage 1990 GD | Precision and aerospace duty — multi-metal, magnesium included | 3–15% v/v · 49–77 °C · minimum 5% on aluminium |
| AquaVantage 815 GD | The precision benchmark where an approval is required, down to oxygen service | 60–66 °C typical, 54–77 °C approved · safe on magnesium, rare in this class |
2 · Baked carbon, varnish and cooked oil
What it is. Oil that went past the point of no return. Held hot for long enough, the chains stop sliding past one another and start bonding to each other instead — cross-linking into a hard, dark, continuous film. Diesel soot and combustion products get trapped in it as it forms.
Why like with like fails here. That film is no longer oil. It has a different chemical identity from the lubricant it started as. A solvent that would have taken the oil off cold, before it cooked, now sits on top and does nothing. A stronger detergent does not help either, because there is nothing left for the surfactant tail to dissolve into.
What takes it off. Hot alkali. It attacks the ester linkages holding the matrix together and breaks the film into fragments the bath can wet and carry away. This is the soap-making reaction, run on a cooked oil film. It depends on temperature as much as concentration: an alkaline decarboniser run warm rather than hot will look like a dud, and the usual first fix on a slow carbon bath is to check the heater, not the dose.
What carries it
| Product | Where it sits | Working conditions |
|---|---|---|
| Desludge | Workshop decarbonising — fuel residues, engine sludge and baked carbon off ferrous components | pH 13, silicate-inhibited so aluminium is protected at working strength · 10–20% v/v · 40–60 °C · not for zinc or magnesium |
| MetalTek 100 | Grease, rust, scale, carbon and paint off steel and cast iron in a single bath | pH 14 · 10–30% v/v · 60–80 °C · ferrous only — attacks aluminium, zinc and tin rapidly |
3 · Paint, powder coat and stoved finishes
What it is. A cured polymer designed to stay on the part for its service life. Chemically it has a lot in common with baked carbon: cross-linked, insoluble and anchored to the surface it was applied to.
Why one chemistry is not enough. Alkali alone works on a stoved finish, but slowly: it can only attack the outside face. A solvent alone swells the film without breaking the chemistry holding it together. Each half does a job the other cannot.
What takes it off. Run them together. The solvent diffuses into the coating and makes it swell, which breaks its grip on the metal and opens the structure up; the alkaline partner then gets into the loosened film and hydrolyses it off. Paint lifts in sheets and flakes rather than dissolving, which is why filtering the bath matters — the residue is solid, and left in there it just circulates.
What carries it
| Product | Where it sits | Working conditions |
|---|---|---|
| The Alloy System ALLOYSolve + ALLOYSalt-L | Stoved finishes, powder coat and baked carbon off aluminium, zinc, steel and cast iron, without attacking the aluminium | Matched volumes mixed, then 10% v/v in water · 40–70 °C, heating required · not for magnesium · the mixed system is non-combustible per its SDS |
| MetalTek 100 | Paint stripping where the part is steel or cast iron and nothing else is in the basket | pH 14 · 60–80 °C · ferrous only |
4 · Rust, oxide and heat scale
What it is. Rust is the part itself, chemically altered: iron that has given up electrons to oxygen and become an oxide. It is ionic and inorganic, so a surfactant has nothing to grip.
Why detergent does nothing. There is no oily phase for the surfactant tail to enter. Run a degreaser at double strength all day and the rust is still there. This is the most common wasted bath we see.
Two routes take it off, and they suit different parts.
Acid. Protons dissolve the oxide lattice and take the iron into solution. Fast and effective. The catch is that the acid cannot tell the oxide from the metal underneath, so once the scale is gone it starts on the part. Acid descaling is a timed operation that ends in a rinse. Nothing is left to soak.
Chelation. A chelating agent has several arms that close around a metal ion and hold it in a soluble cage. It does this without a low pH, so aluminium and zinc survive a chelating bath that an acid one would destroy. The trade is time: allow an hour, not minutes.
What carries it
| Product | Route | Working conditions |
|---|---|---|
| Descale | Acid — oxides, rust and heat scale off steel; passivates stainless | Phosphoric, rated to below pH 1 · 2.5–10% v/v · ambient to 50 °C, never above 60 °C in ultrasonics · time-limit, rinse and neutralise · not for aluminium, zinc, magnesium or painted surfaces |
| CoreKleen HX + CoreKleen Plus | Chelation — red dirt, rust and scale out of cooler cores with no acid pickling | pH 6 · 20% v/v HX with 1–2% v/v Plus · 50–60 °C · 60–90 minutes · safe on aluminium and zinc; not for magnesium |
| MetalTek 100 | Alkaline — takes rust and scale with the grease and carbon in one bath | pH 14 · ferrous only |
5 · Mineral ash and inorganic residue
What it is. What remains in a diesel particulate filter once the carbon has burned away: calcium from the oil additive package, zinc phosphate from anti-wear chemistry, magnesium oxides. It looks like soot. It does not behave like soot.
Why the carbon chemistry misses it. Ash is inorganic. It will not burn off in a regeneration and it will not hydrolyse in an alkaline bath, because there are no organic bonds to break. A core can come out of a thermal clean looking finished and still be substantially blocked with white ash.
What takes it off. The grab mechanism again — an acidic, chelating attack that takes those metal ions into solution and lets them rinse out of the channels.
What carries it
| Product | Where it sits | Working conditions |
|---|---|---|
| RegeniK | Dissolves the mineral ash that carbon cleaning leaves behind — calcium ash, zinc phosphate and magnesium oxides out of DPF cores | Neat · 10–20 minutes · citric-based, passivates stainless · time-limit on carbon steel and cast iron · not for aluminium, zinc, magnesium or brass |
6 · Dirt, dust and solid particulate
What it is. Sand, road grime, swarf, red dirt, carbon dust. Insoluble. Nothing in a parts tank dissolves a grain of silica.
What holds it on. The binder. Particulate rarely sticks to metal by itself; a film of oil or a layer of oxide holds it there. Attack the binder and the dirt lets go. That is why a degreaser clears mud off an engine and an acid clears dirt out of a rusted core. In both cases the chemistry never touched the dirt.
What finishes the job. Cavitation gets the released particles out of blind holes and off internal surfaces. Filtration takes them out of the bath so they are not redeposited on the next load. Chemistry releases, ultrasonics transports, filtration removes. Leave filtration out and the next load is washed in what came off the last one.
7 · What happens after the bath
The oil that was protecting a steel part is the thing you have just removed. Bare ferrous metal coming out of a hot aqueous bath will flash rust while it is still warm and damp. This catches people out on the first clean of a new process and usually gets blamed on the detergent.
A rust inhibitor run in the rinse tank lays down a thin temporary film that holds the part through handling, storage and transport to the next operation. It is not rinsed off afterwards — the film is the whole point, and washing it away undoes the step.
What carries it
| Product | Where it sits | Working conditions |
|---|---|---|
| Anti-Rust | Short-term rust prevention for ferrous parts between cleaning stages | 2–5% v/v in the rinse tank · 1–2 minute dip · ambient to 50 °C · not rinsed off afterwards — the film is the point · not for aluminium, zinc, magnesium, copper or brass |
What pH tells you
pH is read as a power rating, as though 14 were a stronger 12. It is not a scale of strength. pH tells you which mechanism you have bought, and which metals that puts at risk.
“It is not working, so move up to the stronger one.” On baked carbon on steel, a stronger alkali may well be the right call. On rust, no alkali will touch it at any strength, because the mechanism is wrong. And with aluminium or zinc in the basket, moving up a step is how a two-hour job ends in a scrapped component.
| Where the bath sits | What that buys you | What it puts at risk |
|---|---|---|
| Acid — below pH 3 | Dissolves oxides, rust and scale. Passivates stainless | Attacks the base metal once the scale is gone. Not for aluminium, zinc or magnesium. Brass dezincifies |
| Near-neutral — pH 6 to 8 | Chelation and gentle detergency. The safe bath for mixed-metal assemblies and sensitive substrates | Slower. Buys safety with time |
| Mild alkaline — pH 9 to 12 | The general degreasing range. Lifts oils, greases and light carbon across most metals | Aluminium needs a window on dose, temperature and time. Copper and brass tarnish |
| Caustic — above pH 12 | Decarbonising and paint stripping. Breaks cross-linked films that nothing milder will shift | Takes aluminium, zinc, tin and magnesium with the soil unless the formulation is inhibited for it |
So the questions come in a fixed order: what is the metal, then what is the soil, then how hot can the bath run. The metal sets the ceiling, the soil picks the mechanism under it, and temperature is the adjustment left to you.
The rest of the words on the data sheet
The vocabulary you need to read a cleaning data sheet, with the misreading each term usually gets.
| Term | What it means — and what it is not telling you |
|---|---|
| Surfactant | Short for surface-active agent. The molecule described in section 1: oily tail, water-loving head. It is what lets water pick up oil. |
| % v/v | Parts of concentrate in a hundred parts of finished bath, measured by volume. At 10% v/v you add one part of concentrate to nine of water. Over-dosing buys foam, rinse problems and a bigger disposal bill; it does not buy cleaning. |
| Builder | The part of the formula that holds the pH where it needs to be and ties up hardness in the water. The surfactant does the lifting; the builder keeps the conditions right for it to work. It is the first thing cut in a cheap formulation. |
| Chelant · chelating agent · sequestrant | Three names for one thing: a molecule with several arms that closes around a metal ion and holds it in solution. It is how rust comes off without acid, and how hard water is kept from leaving deposits on the parts. |
| Saponification | Alkali splitting a fat or an oil-derived film into pieces that dissolve. The soap-making reaction, and what a decarbonising bath does to baked carbon. |
| Inhibited · inhibitor | An additive that protects the metal from the cleaner. Silicate in an alkaline bath is what lets aluminium survive pH 13. Inhibited means safe inside the dose, temperature and time the sheet states. Outside that window the protection is used up and the metal is exposed. |
| Passivates | Leaves a thin, stable oxide film that resists further corrosion. Phosphoric and citric acids passivate stainless — which is why they are used on it — and the same acids will keep eating plain carbon steel once the scale is gone. |
| Emulsifying · demulsifying | Whether the bath holds the oil in suspension or lets it split out and float so you can skim it off. On an oily-parts operation this single choice decides bath life and disposal cost more than anything else on the sheet — it is worth its own page. |
| Free alkalinity · titration | How bath strength is measured. A bath that looks fine can be well under strength, because what gets used up is the active chemistry and not the colour. Any process under a cleanliness standard needs titrating on a set interval. |
Soil, mechanism, where to start
| What is on the part | Mechanism | Where to start |
|---|---|---|
| Oil, grease, cutting fluid, light handling soils | Dissolve — surfactant | FX Degreaser · AquaVantage 1696 GD where the metals are sensitive |
| Heavy grease and tenacious soil on steel, aluminium or titanium | Dissolve — heavy-duty surfactant | AquaVantage 815 QR-NF |
| Precision, aerospace and approval-driven work | Dissolve — inhibited multi-metal | AquaVantage 815 GD · AquaVantage 1990 GD |
| Baked carbon, varnish, engine sludge | Change — hot alkaline hydrolysis | Desludge · MetalTek 100 if the part is ferrous only |
| Paint, powder coat, stoved finishes | Change — solvent swells, alkali lifts | The Alloy System · MetalTek 100 on ferrous |
| Rust and heat scale on steel | Grab — acid | Descale, timed and neutralised |
| Rust, scale and red dirt on mixed metals and cooler cores | Grab — chelation at near-neutral pH | CoreKleen HX with CoreKleen Plus |
| White mineral ash in DPF cores | Grab — acidic chelation | RegeniK, neat |
| Flash rust on clean ferrous parts | Protect | Anti-Rust, as a dip off the rinse |
Parts with more than one soil on them
Most parts arrive with several. A cylinder head carries oil, carbon, scale and paint on the same aluminium casting, and no single bath takes all four without taking the casting as well. That is a sequence to design: which mechanism runs first, what the part is rinsed into between stages, and where the protection step sits at the end.
A data sheet lists the metals a chemical is proven on and the window it works in. It cannot know what the soil on your parts has been through, how long it has been sitting, or what the last process left behind. That part comes out of running it.
Questions we get asked
What removes baked-on carbon from engine parts?
Hot alkali. Once oil has cooked onto a part it is no longer oil, so no solvent and no detergent will dissolve it. An alkaline decarboniser breaks the cross-linked film into fragments the bath can carry away. Desludge runs at 10–20% v/v and 40–60 °C and is silicate-inhibited so aluminium survives it. MetalTek 100 is stronger at pH 14 and 60–80 °C, but ferrous parts only.
Why is my degreaser not removing rust?
Because rust is not a soil sitting on the part — it is the part, chemically altered into an oxide. There is no oily phase for a surfactant to grip, so a degreaser has no point of attack at any strength. Rust needs an acid or a chelating agent.
How do you remove rust without acid?
Chelation. A chelating agent closes around the metal ion and holds it in solution without needing a low pH, so aluminium and zinc survive a bath that an acid would destroy. CoreKleen HX with CoreKleen Plus runs at pH 6, 50–60 °C, for 60–90 minutes. It takes longer than acid and it does not pickle the part.
What strips paint off aluminium without attacking the metal?
A two-part system. A benzyl-alcohol solvent swells the cured film and breaks its grip, and an alkaline partner then lifts and hydrolyses it. Neither half works alone. The Alloy System runs at 10% v/v of the mixed system, 40–70 °C — heating is required — and is safe on aluminium, zinc, steel and cast iron, but not on magnesium.
Does a higher pH clean better?
No. pH tells you which mechanism you have bought and which metals that puts at risk, not how strong the product is. Moving from pH 12 to pH 14 will not touch rust, because the problem there is mechanism rather than strength — and with aluminium or zinc in the basket it is how a part gets scrapped.
What does non-ionic mean on a cleaning chemical?
It describes the electrical charge on the water-loving end of the surfactant molecule, and nothing else. Non-ionic means no charge, which gives low foam and tolerance of hard water. That matters in an ultrasonic tank because foam is air, and air does not cavitate. It says nothing about strength, metal safety, temperature or rinsing.
What temperature should an ultrasonic cleaning bath run at?
Hot enough to thin the soil, below the point where cavitation weakens. Oil viscosity falls sharply with heat, so the same detergent does work at 60 °C it cannot do at 25 °C. Past roughly 70 °C cavitation falls away as the liquid starts flashing to vapour. On aluminium the bath stays at or below 60 °C.
What dissolves the white ash left in a diesel particulate filter?
An acidic chelating wash. The ash is calcium, zinc phosphate and magnesium oxides left behind once the carbon has burned off — inorganic, so it will not burn and will not hydrolyse. RegeniK is used neat for 10–20 minutes. A core can look finished after a thermal clean and still be substantially blocked with ash.
What is a chelating agent in a cleaning chemical?
A molecule with several arms that closes around a metal ion and holds it in a soluble cage. It is how rust and scale come off without acid, and how hard water is kept from leaving deposits on the parts. Chelant and sequestrant are the same thing.
Why do my steel parts rust straight after cleaning?
Because the oil that was protecting them is what you just removed. Bare ferrous metal coming out of a hot aqueous bath flash rusts while it is still warm and damp. A rust inhibitor run in the rinse tank at 2–5% v/v, 1–2 minutes, lays down a temporary film. It is not rinsed off afterwards — the film is the point.
What does % v/v mean on a cleaning data sheet?
Parts of concentrate in a hundred parts of finished bath, measured by volume. At 10% v/v you add one part of concentrate to nine of water. Over-dosing buys foam, rinse problems and a bigger disposal bill; it does not buy cleaning.
Read next
Validating the process on your own parts
We assess each application. Where required, we validate the process through a controlled cleaning trial on the machine and chemistry we would specify, with the cycle and the result reported against your standard — ask us to scope it.