The mechanism
Atmospheric corrosion does not require visible water. It proceeds in an electrolyte film only a few molecular layers thick that condenses onto the surface out of the ambient humidity. Anyone specifying temporary corrosion protection therefore needs three quantities: when that film forms, what makes it more conductive, and how it is kept away from the metal. Everything else on this page follows from those three.
What happens electrochemically
Atmospheric corrosion of iron is oxygen corrosion in a thin-layer electrolyte. Iron dissolves at the anode; at the cathode, oxygen dissolved in the water film is reduced to hydroxide ions. Electrons travel through the metal and ions through the electrolyte; the circuit therefore closes inside the component itself, which is exactly why a water film a few molecular layers thick is enough. The dissolved iron ions go on to form the familiar hydrated iron oxides. Rust is the product, not the cause.
Anode and cathode are not far apart. They form as local cells on one and the same surface: at microstructural differences, at inclusions, at cold-worked zones, at cut edges and underneath dirt particles. That is why a component rusts first where it was machined, blasted or handled, and not evenly across the face. Terminology and the classification of corrosion types are set out in ISO 8044:2024, published in Germany as DIN EN ISO 8044:2025-05; this standard superseded the former DIN 50900 series.
When humidity becomes an electrolyte
What matters is not visible wetness but relative humidity. W. H. J. Vernon showed as early as 1935 that corrosion begins well below 100 per cent relative humidity, and the concept of a critical humidity goes back to that work. For iron, the corrosion literature gives an empirical critical relative humidity of around 60 per cent: above it, a continuous water film of several molecular layers forms and the electrochemical reaction starts. A second step is described between 75 and 80 per cent and attributed to capillary condensation in the pores of corrosion products that have already formed. That is the physical reason why rust accelerates once it has started.
The packaging handbook published by the German insurers' association (GDV) sets the practical threshold more conservatively: corrosion can begin above 40 per cent relative humidity and increases rapidly above 60 per cent. The two statements do not contradict each other. The 60 per cent figure applies to clean surfaces in unpolluted air; the 40 per cent figure allows for hygroscopic contamination. Critical humidity is not a constant of nature: hygroscopic salts on the surface lower it, because they take up water at lower humidity and form a conductive solution. That is why chlorides are so dangerous: from marine air, from de-icing salt, from perspiration on bare hands, or from process water.
One figure is routinely miscited here. ISO 9223:2012 works with the time of wetness and defines it as relative humidity above 80 per cent at a temperature above 0 °C. That is a different threshold for a different purpose: it classifies atmospheres, it does not describe the onset of the reaction. The 60 per cent figure comes from the technical literature and is not a standardised value.
Dew point and condensation inside the packaging
As air cools, its capacity to hold water vapour falls. At the dew point, relative humidity reaches 100 per cent; cooling further, water condenses out. It condenses on any surface colder than the dew point of the air touching it. Inside a package or a sea container that is often the enclosure: container roof, crate lid or sheet-metal casing cool down faster overnight than the goods inside, and the condensate drips from there onto the component. It can just as easily be the component itself. A heavy steel part holds its temperature for hours; brought out of chilled storage, or out of a cold night into warmer and more humid air, it is the first thing to mist over, even when the packaging has long since warmed up. Two practical consequences follow. First, the temperature and humidity logger belongs inside the package and not only in the container, because only there does it become visible which surface drops below the dew point. Second, a cold component is left to acclimatise inside its packaging before unpacking, preserving or further processing; opening it straight away creates precisely the water film the whole chain was built to prevent. A component packed while still warm brings its own condensate with it: the trapped air and the moisture held in timber, paper and cardboard stay inside the package. Shipping across climate zones therefore means packing a moisture reservoir along with the part.
The four forms that actually occur in production
- General corrosion and flash rust. Shallow attack across the face after brief exposure to moisture. Cosmetic, but the usual trigger for rework and complaints.
- Pitting. Localised attack, driven above all by halide ions such as chloride that break down the passive layer locally. For stainless steels this is the real hazard, because the surrounding surface still looks intact.
- Crevice corrosion. In narrow gaps such as threads, fits, welded overlaps and the space under adhesive tape and labels, the electrolyte becomes depleted in oxygen and the crevice turns anodic. A protective film that does not creep into the gap does not protect there.
- Galvanic corrosion. Where two metals of different electrochemical potential touch in the presence of an electrolyte, the less noble one becomes the anode and dissolves preferentially. This matters at steel-to-aluminium and steel-to-copper-alloy pairings, at stainless fasteners in aluminium, and wherever parts are stacked on damp steel pallets.
Why fingerprints are a starting point
Perspiration contains water, chlorides, lactic acid and urea. It therefore delivers the electrolyte, the depassivating chloride and a hygroscopic residue in one go. That is all three conditions from the first subsection, concentrated on one small area. The print reproduces as a pattern because that is precisely where the critical humidity is locally undercut.
Preserve after the last manual handling operation, never before. Work with gloves from that point on.
The protection principles
Barrier. An oil, wax or dry film separates metal and atmosphere mechanically. It keeps oxygen and water away for as long as it stays closed. Film type and film thickness determine both handling and protection period: an oily film creeps, wets crevices and stays non-tacky but has to be removed; a waxy film is thicker and more robust, lasts longer and calls for a more demanding degreasing step; a dry, transparent film allows labelling and handling without glove marks but has less reserve against mechanical damage.
Inhibition. Inhibitors are polar molecules that adsorb onto the metal surface with their functional group while the non-polar tail points outward. They displace water from the interface and suppress either the anodic or the cathodic half-reaction. An inhibitor therefore acts at the interface rather than through film thickness. That is why very thin inhibited films achieve considerably more than a plain oil of the same thickness.
Dewatering. After aqueous machining, cleaning or rinsing, water remains in crevices, blind holes and threads. Dewatering fluids contain strongly adsorbing, surface-active components that lift the water off the metal; the water coalesces, settles and is separated out in the tank, leaving an inhibited protective film behind. The German technical rule TRGS 615 (May 2007 edition) lists this group explicitly as water-immiscible organic liquids that displace water and leave corrosion-inhibiting thin films. The point is process-critical: a preservative oil without dewatering capability, applied to wet parts, seals the water in underneath the film. At that point the protective film itself becomes the cause.
Vapour corrosion inhibitors (VCI). VCI actives sublime out of a carrier (paper, film, foam, emitter or oil), distribute inside the closed package and deposit on every reachable metal surface, including cavities no spray jet will find. The GDV packaging handbook gives an effective life of up to two years, a maximum distance of 30 cm between VCI material and goods, and a dosage of roughly 40 g of active per cubic metre of enclosed air. TRGS 615 adds that protection only develops at 10 °C and above. That point is routinely overlooked in winter shipping.
Desiccants. Instead of coating the metal, the enclosed air is dried. The German standard DIN 55474:2015-03 sets out the calculation; one desiccant unit as defined in DIN 55473:2021-07 adsorbs at least 3.0 g of water vapour at 20 per cent relative humidity and at least 6.0 g at 40 per cent. This only works inside a barrier-foil enclosure. Desiccant inside a breathable wrapping is money spent for nothing.
Passivation. Converting the surface into a stable layer, for instance by black oxide treatment, is not temporary protection in the narrow sense. A black oxide layer is microporous and has little corrosion resistance on its own; it needs a post-treatment that seals the pores.
Sources: ISO 8044:2024 (DIN EN ISO 8044:2025-05) for terminology and the classification of corrosion types; ISO 9223:2012 for the definition of time of wetness; TRGS 615 (May 2007), clause 2, for the product groups including dewatering fluids and for VCI protection from 10 °C; GDV packaging handbook (accessed 9 August 2026) for VCI spacing and dosage, humidity thresholds and desiccant units; DIN 55473:2021-07 and DIN 55474:2015-03 for the desiccant unit and its calculation; W. H. J. Vernon, Trans. Faraday Soc. 31 (1935), as the conceptual source for critical humidity. The figure of roughly 60 per cent is an empirical value from the corrosion literature and expressly not a standardised value.
↑ Back to contentsIn production
On the shop floor it is not the product that decides the outcome but the chain. That chain has five links, and any one of them can undo the protection even when the other four are right. The most common reason a preservative "did not hold" is a gap in the film or a wet component underneath it, not a weak inhibitor.
Five links, five places to fail
One: the condition before preservation. Is the part dry or still wet, clean or carrying emulsion residues, chips and blasting media? A protective film over a residue of water-miscible metalworking fluid preserves the residue along with the part. For parts that are still wet there are two workable routes: a controlled drying step that can be demonstrated in series production, or a dewatering product that lifts the water off the surface during application itself. Which one is right depends on geometry (blind holes, threads, crevices), throughput, the drying equipment available, and whether drying success can be evidenced reproducibly. What does not work is the third variant: a plain preservative oil on a component whose residual moisture nobody has checked. How emulsion residues and residual water arise in the first place, and how to keep them small, is covered on the page about metalworking fluids.
Two: the application method. TRGS 615 names dipping, spraying, brushing and roller coating for these product groups. In practice the method often governs the achieved protection period more strongly than the formulation does. Dipping reaches bores, threads and crevices and delivers a closed film. Spraying creates a shadow zone at every undercut. Brushing is clean on one-offs but not reproducible in series. Flooding sits between the two.
Three: flash-off and handling. Solvent-based products need to flash off before parts are stacked or packed. Stacking too early presses the film away at the contact points and traps solvent at the same time.
Four: the packaging. Barrier alone, barrier plus VCI, or a barrier-foil enclosure plus desiccant. For sea freight the combination is the rule, not the exception. Packaging therefore belongs in the protection specification and is not an afterthought for the logistics department.
Five: transport and storage. Indoor storage, covered outdoor storage and sea freight across several climate zones differ in severity by orders of magnitude. By how much is set out below.
Film type and downstream process belong together
The question "which film" is always also the question "what happens next". A thin oily film can be removed in an aqueous alkaline wash and is the right choice for interim storage between two machining steps. A waxy film lasts longer but requires a defined degreasing step. A transparent dry film allows labelling and handling without glove marks, at the cost of less reserve against mechanical damage.
Compatibility has to be settled in advance as well. Elastomers and seals can swell in hydrocarbons. Solvent-based products attack some paints and plastics, ABS, polycarbonate and polystyrene in particular. Copper alloys react sensitively to certain inhibitor chemistries, which is why dedicated formulations for non-ferrous metals exist. And not every preservative is compatible with VCI film; in combined systems that is a release of its own.
The most expensive mistake is a film that will not come off reliably
Residues of a preservative oil under a paint layer cause loss of adhesion and undercreep. In welding they produce porosity, spatter and fume. In bonding they form a release layer at exactly the place where the joint has to carry load. In electroplating or powder coating they cause cratering and wetting defects. What makes this so awkward is that the cause is looked for at the end of the chain: the investigation runs in the paint shop while the decision was made at the preservation station.
Whoever selects the preservative therefore has to know the cleaner and the cleaning process already. Preservative and cleaner are released as a pair and re-evidenced whenever either one changes, and that means a defined residual-film test rather than visual inspection. Which cleaner fits in a given case depends on component geometry, material, plant engineering and the downstream process; that is settled by application engineering together with the plant, not by a product recommendation on an overview page.
Protection period: a statement only with its conditions
How quickly unprotected metal is attacked is described by ISO 9223:2012 through corrosivity categories. The standard gives the corrosion rate for the first year of exposure, measured on standard specimens and expressed either as mass loss or as thickness loss. For unalloyed carbon steel the thickness loss ranges from at most 1.3 µm per year in C1 through 1.3 to 25 µm in C2, 25 to 50 in C3, 50 to 80 in C4, 80 to 200 in C5, up to more than 200 and at most 700 µm per year in CX. Between a climate-controlled indoor store and an offshore location there are therefore a good two orders of magnitude. The same preservation is over-specified in one case and inadequate in the other.
Two qualifications belong with this, or the table gets over-used. First, the values apply to standard specimens of a defined material, not to your component with its geometry, its microstructural condition and its surface preparation. Second, the first-year rate cannot be extrapolated linearly: corrosion product layers change the attack over time. The categories rank locations relative to one another; they do not replace an exposure trial.
For sea freight, add what the GDV packaging handbook describes: high salt content in water and air, severe temperature swings when crossing climate zones, and the condensation inside the packaging that follows from them. A defensible statement is therefore never "protects for twelve months" but "protects for twelve months in indoor storage, with an undamaged film and no condensation". The sea route needs a separately specified statement of its own.
Never accept a protection period without its conditions. A figure with no storage category, no film condition and no condensation assumption cannot be verified and is therefore worthless when a claim arrives.
How to qualify a protection period properly
The defensible answer to "how long will it last here" is in no data sheet. It comes from an exposure trial under your own conditions, and the effort involved is smaller than that of a single sea-freight complaint. A qualification plan that holds up in a dispute has five components.
The five components, and the figures inside them, are a site-level arrangement. They follow from the subject matter and not from a standard: we are aware of no standard that prescribes such a plan. That is why the reasoning is set out alongside each figure. A reader who knows where a number comes from can adapt it to their own batch sizes, protection period and inspection budget; a number without an origin can only be believed or discarded.
- Reference parts that represent the worst case. Not the simplest part, but the one with deep blind holes, threads, fits, cut edges, rack contact points and mixed material pairings. Set at site level: at least three identical parts per checkpoint. With one part every finding is an isolated case; with two, a deviation cannot be placed; from three onwards it becomes possible to tell an outlier from a trend. Anyone able to inspect more parts gains certainty. Each reference part is photographed before preservation, with batch, upstream process and the residual-moisture finding recorded.
- Preservation and packaging exactly as in series. Same application method, same flash-off time, same stacking, same packaging including VCI material, desiccant quantity, film and closure. A qualification produced by careful manual work proves nothing about a series that sprays and stacks immediately.
- The real route, not a sample store. The reference parts travel inside a genuine shipment, with a temperature and humidity logger inside the package and not merely in the container. The qualification is repeated whenever route, season, packaging, carrier or transhipment point changes.
- Checkpoints instead of one final date. Set at site level: an interim assessment at roughly a quarter and again at roughly half of the intended protection period, plus the assessment on arrival. The position of the two points is reasoned from the subject matter and not derived from a standard. The first lies early enough for an early failure to show up while the consignment is still in transit; the second turns two isolated findings into a direction, instead of delivering only a final state at the end. Looking only at the end leaves you unable to tell, after a failure, whether protection lapsed after two weeks or after five months, and therefore unable to tell which link in the chain to change.
- Acceptance criteria fixed in writing beforehand. Typically: no corrosive attack on functional and sealing faces; a stated limit on non-functional faces, for which rust grades A to D in ISO 8501-1:2007 provide a nameable scale; no condensate inside the package; a closed film at the defined reference locations; and a passed residual-film test after the intended cleaning step. These criteria are agreed before the trial, not negotiated after it.
The result is a protection period that carries its own conditions (route, packaging, climate band and the reference part it was assessed on) and that consequently holds up when a complaint arrives. That is the difference between an evidenced statement and a number.
Sources: TRGS 615 (May 2007), clause 2, for the application methods and the product groups; ISO 9223:2012, Table 2, for the corrosion rates of unalloyed carbon steel in the first year of exposure across categories C1 to CX; ISO 8501-1:2007 for rust grades as an assessment scale; GDV packaging handbook (accessed 9 August 2026) for salt loading, climate zone changes, condensation in sea transport and the unpacking inspection on reference parts. The qualification plan itself is a site-level arrangement; we are not aware of a standard that prescribes it.
↑ Back to contentsWhat it is worth
Corrosion protection pays back in four currencies, and none of them is called "protection". It always strikes the most expensive inventory stage: a component that already carries the full value added. That is what separates a preservation step managed as a cost item from one understood as a risk item.
Scrap and rework
A patch of flash rust on a finished functional surface means reworking, regrinding or scrapping. Unlike a dimensional error in the first set-up, it appears at the end of the process chain, once set-up time, tooling and inspection effort have all been paid for. The material value is usually the smallest part of the loss.
Complaints and delivery reliability
Rust is the defect a customer identifies without any measuring equipment, photographs and complains about. A complaint out of a sea-freight consignment costs the value of the parts plus a second freight charge, a missed date and part of the trust. Anyone shipping across climate zones is not buying packaging with the packaging specification; they are buying schedule reliability.
Process costs further downstream
A film that comes off reliably keeps the cleaning step short and the paint or bonding line stable. A film that does not creates adhesion problems whose cause is hunted in the wrong department, with a correspondingly long investigation. The decision about removability is taken weeks earlier and is rarely booked where it takes effect.
Inventory flexibility
A plant that can preserve reliably can produce to stock and decouple batch sizes from call-off dates. Without dependable protection, production has to follow the call-off, which drives set-up cost and forces small batches. Preservation is therefore a precondition of production control and not merely a surface topic.
Source: this assessment follows from the relationships evidenced in the sections above, in particular the corrosivity categories of ISO 9223:2012. We do not quote percentage savings: we hold no robust, publishable operating data for them.
Your application
Indoor storage, outdoor storage or sea freight?
The three tasks call for different protection systems. From your details on the component, the upstream process, the storage location, the transport route and the downstream process we build a technical classification, not a product list from the catalogue.
Risks
The risks of temporary corrosion protection sit in two places. At the component, a wrongly placed preservation can conceal damage instead of preventing it; whether it does is decided by the process, not by the product alone. At the workplace, solvents, aerosols and the formation of N-nitrosamines have to be assessed. The second is the more uncomfortable one, and it is the reason this product group has a technical rule of its own in Germany.
The film that seals the problem in
If preservation is applied over a wet, salt-laden or contaminated surface, the electrolyte stays underneath the barrier. Corrosion then continues out of sight, and the damage only becomes visible on unpacking, at the customer and not in your own works. This is the most expensive failure mode on this page, because it bypasses inspection in your own house.
That does not settle the question in the abstract, though. Whether a film rescues the situation or makes it worse depends on the type and quantity of contamination, on the water-displacing and creeping ability of the product used, and on whether that particular combination of surface condition and product has been qualified. A dewatering product is designed for the wet case and can control it. What remains without that evidence is an uncontrolled risk: preserving over an unverified surface condition is not a protective measure, it is an assumption.
Gaps and contact faces
Rack contact points, lifting points, drip edges and the areas under tape or labels are systematically under-supplied. The gap under a label is a textbook case of crevice corrosion: oxygen-depleted, electrolyte-bearing and out of reach of any spray jet.
When the packaging becomes the cause
Damp timber, acidic papers, unsuitable plastics and bare steel pallets can make the situation worse rather than better. Mixed packing of steel and aluminium parts creates galvanic couples as soon as condensate appears. And VCI systems are not automatically released for every material group.
N-nitrosamines: the uncomfortable point
Corrosion preventives can contain secondary amines. If nitrosating agents are added, such as nitrite, nitrogen oxides or nitrous acid, carcinogenic N-nitrosamines can form. The German technical rule TRGS 615 (May 2007) governs precisely this case and names the entry paths concretely: exhaust from combustion engines and from gas- or diesel-powered fork-lift trucks, welding equipment, tobacco smoke, nitrite-bearing cleaners and hardening salts, bought-in parts pre-preserved with nitrite-containing media, as well as the bacterial reduction of nitrate to nitrite in aqueous systems. Formation is favoured by high concentrations of the reactants, elevated temperatures, acidic pH (the optimum usually lies between pH 2 and pH 5) and by applications that generate aerosol. Anyone running water-mixed corrosion protection emulsions in a circulating system therefore has the same monitoring task as in the care of water-miscible metalworking fluids.
Skin contact
TRGS 615 requires skin contact to be limited by technical means to what is unavoidable, refers to TRGS 401, and points out that substantial dermal absorption has to be expected for a number of N-nitrosamines. Solvent-based products additionally defat the skin. Assessing the dermal hazard, selecting suitable gloves and drawing up the skin protection plan are the plant's responsibility under TRGS 401 (October 2022 edition, last amended September 2024).
Solvents, fire and emissions
Solvent-based preservative oils bring a flash point, a solvent load and, when sprayed, an aerosol fraction. Spray booths need extraction, freedom from ignition sources and an assessment of explosive atmospheres, and the flash-off zone has to be included, not just the booth itself. Classification, labelling and the disposal of oil-bearing wash and rinse baths follow from the applicable safety data sheet and from the risk assessment under the German Gefahrstoffverordnung (Hazardous Substances Ordinance). Readers outside Germany should apply the equivalent national implementation of the EU chemical agents and carcinogens directives. This page gives no legal advice.
False confidence from test figures
The neutral salt spray test to ISO 9227:2022 (with Amd 1:2024) runs under constantly severe conditions: no drying phases, no ultraviolet exposure, no temperature cycling. The results are suitable for ranking formulations, not for predicting storage life; the poor transferability of accelerated laboratory tests to field behaviour is documented in the literature. The standard also covers three procedures: neutral salt spray, acetic acid salt spray and copper-accelerated acetic acid salt spray. An hours figure without the procedure and the test set-up is not comparable between two laboratories. The defensible question to a supplier is therefore not "how many hours" but "by which procedure, on which substrate, at which application rate, and where is the test report".
Microbiology in water-mixed systems
Water-miscible corrosion protection emulsions are growth media just like any water-mixed metalworking fluid. Bacterial growth lowers the pH, destroys inhibitors and, by reducing nitrate, generates exactly the nitrite you do not want in an amine-bearing system. Microbial monitoring is therefore not a hygiene topic but part of nitrosamine prevention.
Sources: TRGS 615 (May 2007), clauses 3.2 to 3.6 for the mixing prohibition, entry paths and skin contact, and clauses 4.2, 4.3 and 5.1 to 5.4 for limits and monitoring; TRGS 401 (October 2022, last amended GMBl 2024 p. 769) for assessing the dermal hazard; the German Gefahrstoffverordnung as amended 17 December 2025 for risk assessment and protective measures; ISO 9227:2022 + Amd 1:2024 for the three salt spray procedures; Q-Lab and the review paper listed under Sources for the correlation between accelerated testing and field performance.
↑ Back to contentsPreventive measures
The table below is built so that it can be transferred into an inspection instruction: what is measured or checked, at what interval, against which criterion, and where that criterion comes from. Where a row says "site-level arrangement", no applicable rule exists; the plant then has to set and document the criterion itself. The emphasis lies deliberately on TRGS 615, because for this product group it provides the densest and most binding numerical basis. It is German law and applies to workplaces in Germany; readers elsewhere should treat it as a well-documented state of the art and check their own national requirements.
| Parameter / check | Interval | Criterion | Governing rule |
|---|---|---|---|
| Condition before preservation | every batch | surface free of emulsion, salt and particulate residues; residual moisture verified. For parts still wet, either a validated drying step or a dewatering product; a plain preservative oil requires a demonstrably dry surface | TRGS 615, clause 2 (product groups); the choice between drying and displacing is a site-level arrangement |
| Film application | start of shift and after every process change | application rate by differential weighing on reference parts; visual check for gaps at contact points, undercuts and drip edges | site-level arrangement; methods per TRGS 615, clause 2 |
| Climate at the storage location | continuously, with a data logger | relative humidity, temperature and margin to the dew point; corrosion is possible above 40 % RH and increases rapidly above 60 % | GDV packaging handbook; critical humidity per the corrosion literature |
| Corrosivity of the location | on change of location or use | classification C1 to CX; corrosion rate of unalloyed carbon steel in the first year of exposure, as thickness loss on standard specimens: at most 1.3 µm/a in C1 up to more than 200 and at most 700 µm/a in CX | ISO 9223:2012, Table 2 |
| Qualification of the protection period | at first release and on change of route, season, packaging or preservative | reference parts with the least favourable geometry travel inside a real shipment, logger inside the package; assessment at two interim points and on arrival against acceptance criteria fixed in writing beforehand | site-level arrangement; rust grades per ISO 8501-1:2007; unpacking inspection per the GDV packaging handbook |
| Comparing two preservatives | on change of formulation or supplier | salt spray test stating procedure (NSS, AASS or CASS), substrate, application rate and duration; without these an hours figure is not comparable | ISO 9227:2022 + Amd 1:2024 |
| Humidity exposure without salt | on change of formulation or supplier | testing in a condensation climate or humidity cabinet | ISO 6270-2:2017; ASTM D1748-24 |
| Desiccant sizing | per packaging specification | calculated from volume, tightness, material moisture and transit time; one desiccant unit adsorbs at least 3.0 g of water vapour at 20 % RH and 6.0 g at 40 % | DIN 55474:2015-03 for the calculation, DIN 55473:2021-07 for the sachet (German standards) |
| Barrier foil | goods inwards and supplier release | water vapour transmission rate against the contractually agreed limit; without a tight enclosure any quantity of desiccant is too small | ISO 15106 series; the measuring principle determines the applicable part (the former DIN 53122-2 was superseded by ISO 15106-3). Fix method and limit in the purchase contract |
| VCI application | per packing instruction | distance from VCI material to goods no more than 30 cm; dosage roughly 40 g of active per m³ of enclosed air; protection only from 10 °C upwards | GDV packaging handbook; TRGS 615, clause 2 |
| Secondary amines in the product used | goods inwards, review of the safety data sheet | no more than 0.2 % in the finished product; no more than 0.02 % for VCI packaging materials containing up to 10 % active substance | TRGS 615, clauses 4.2 and 5.1 |
| Nitrite and other nitrosating agents | goods inwards, review of the safety data sheet | for VCI materials, greases, waxes and water-immiscible liquids, more than 1.0 % nitrite (as sodium nitrite) or more than 0.1 % of other nitrosating agents is permissible only with monitoring, and reduction below 0.5 % is to be sought; water-miscible and water-mixed products are nitrite-free as supplied | TRGS 615, clause 4.3 |
| N-nitrosamines in air | regularly, where the product contains secondary amines above those limits | state of the art: 0.2 µg/m³ for the nitrosamine that can form from the secondary amine in use | TRGS 615, clauses 5.2 and 5.3; measurement per TRGS 402 (September 2023) |
| N-nitrosamines in circulating baths | every 6 months below half the limit, every 3 months between half the limit and the limit | N-nitrosodiethanolamine no more than 5 mg/kg, N-nitrosomorpholine no more than 1 mg/kg in the corrosion preventive | TRGS 615, clause 5.4 |
| Mixing and carry-over | permanently, set out in the operating instruction | products containing secondary amines must not be mixed with nitrite-bearing preparations; carry-over from fork-lift exhaust, welding fume, nitrite-bearing cleaners, hardening salts and pre-preserved bought-in parts must be prevented | TRGS 615, clauses 3.2 to 3.4; GefStoffV, Annex IV No. 31 |
| Skin contact | permanently | limit skin contact technically to what is unavoidable; derive suitable gloves and a skin protection plan from the risk assessment | TRGS 615, clause 3.6; TRGS 401 (October 2022, amended 09/2024) |
| Removability of the film | at process release and after any change to preservative or cleaner | residual-film test after the defined cleaning step, for example a water-break test or a gravimetric residual extract determination | site-level arrangement |
| Unpacking inspection | on every first shipment over a new route | inspect reference parts for condensate, incipient rust and film condition, and record the result | GDV packaging handbook |
| Wood packaging for export | per export shipment | timber from 6 mm thickness heat-treated to a core temperature of 56 °C for at least 30 minutes, with the IPPC mark and a registered producer | ISPM 15 (IPPC/FAO) |
Sources: TRGS 615 (May 2007, GMBl 2007 p. 574) for all limits, intervals and use restrictions; TRGS 402 (September 2023) for determining inhalation exposure; TRGS 401 (October 2022, amended 09/2024) for skin protection; ISO 9223:2012, ISO 9227:2022 + Amd 1:2024, ISO 6270-2:2017, ASTM D1748-24, DIN 55473:2021-07 and DIN 55474:2015-03 for the test and design methods; GDV packaging handbook (accessed 9 August 2026) for climate, VCI and the unpacking inspection; ISPM 15 for the treatment of wood packaging.
↑ Back to contentsStandards and rules
The editions listed below were current on 9 August 2026. Standards are withdrawn, superseded and renamed; check for a more recent edition before relying on them. Where a German national rule is cited, that is stated; such rules are binding for workplaces in Germany and elsewhere serve as a well-documented state of the art.
| Designation | Edition | Cited for |
|---|---|---|
| TRGS 615 (German technical rule for hazardous substances) | May 2007, GMBl 2007 p. 574 | use restrictions for corrosion preventives that can give rise to N-nitrosamines: product groups, application methods, limits, monitoring intervals, VCI from 10 °C |
| TRGS 401 (German) | October 2022, last amended GMBl 2024 p. 769 | hazards from skin contact: determination, assessment, measures |
| TRGS 402 (German) | September 2023, GMBl 2023 p. 898 | determining and assessing inhalation exposure |
| GefStoffV (German Hazardous Substances Ordinance) | as amended 17 December 2025 | risk assessment and protective measures; Annex IV No. 31 prohibiting products that contain both secondary amines and nitrosating agents |
| ISO 8044 (DIN EN ISO 8044:2025-05) | ISO 8044:2024 | terminology and classification of corrosion and corrosion types; supersedes the DIN 50900 series |
| ISO 9223 | 2012 | corrosivity categories C1 to CX with corrosion rates for the first year of exposure; definition of time of wetness |
| ISO 9227 | 2022, with Amd 1:2024 (DIN EN ISO 9227:2024-10) | salt spray tests NSS, AASS and CASS as comparative tests |
| ISO 6270-2 | 2017 (DIN EN ISO 6270-2:2018-04) | resistance to humidity, part 2: condensation |
| ASTM D1748 | D1748-24 (November 2024) | rust protection by metal preservatives in the humidity cabinet |
| ISO 15106 series | current parts by measuring principle | water vapour transmission rate of barrier films; ISO 15106-3 superseded the former German DIN 53122-2 |
| DIN 55473 / DIN 55474 (German) | 2021-07 and 2015-03; both listed as current editions by DIN Media | desiccant sachets and the definition of the desiccant unit; calculation of the number of units required |
| ISPM 15 (IPPC/FAO) | internationally applicable | treatment of wood packaging material in international trade |
| ISO 12944-2 | 2017 (DIN EN ISO 12944-2:2018-04) | for delimitation only: long-term corrosion protection by paint systems, not temporary preservation |
| ISO 11997-3 / VDA 233-102 | 2022 (DIN EN ISO 11997-3:2024-01) and 06/2013 | cyclic corrosion testing, mainly in automotive supply; only indirectly relevant to temporary preservation |
| ISO 8501-1 | 2007 (DIN EN ISO 8501-1:2007-12), revision in draft | rust grades A to D and surface preparation grades |
| DIN 51360-2 (German) | 1981-07, listed as the current edition by DIN Media | for delimitation only: the chip/filter paper corrosion test for water-mixed metalworking fluids. The Herbert test is DIN 51360-1; the two are frequently confused. We deliberately give no edition status for Part 1, because it was not available to us from an authorised standards source |
| GDV packaging handbook | continuously maintained, accessed 9 August 2026 | corrosion protection methods, VCI dosage and spacing, desiccant sizing, the specifics of sea transport |
Three designations that turn up regularly in searches on this subject expressly do not belong here. DIN 55476 could not be substantiated; DIN 55510 deals with the modular coordination of packaging dimensions and not with corrosion protection; and the ISO 21227 series evaluates coating defects by optical imaging and has nothing to do with VCI. We found no dedicated German rule specifically for VCI testing. That means "not found", not "does not exist".
Not a substitute for your risk assessment. This article describes the general state of the art and the applicable body of rules. It does not replace the risk assessment required under section 6 of the German Hazardous Substances Ordinance (GefStoffV) and TRGS 400, nor the operating instructions, staff instruction, or any product-specific approval. For each product, the current safety data sheet and technical data sheet prevail, together with the arrangements in force at your site. Responsibility for selection, operating conditions, monitoring and documentation rests with the employer.