SurTecCorrosion Protectionparts2clean Forum.2012

What is temporary corrosion protection Systems for temporary corrosion protection Jens Emmerich, SurTec Deutschland GmbH, Fachforum parts2clean, 25.10.2012 SurTec International GmbH

Why Corrosion Protection? 

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Preven Preventio tion n of damage damages s by corros corrosion ion on met metall allic ic parts parts Preven Preventio tion n of econo economic mical al damage damages, s, e.g. e.g. high high rejec rejectio tions ns or custo customer mer complaints Preventio Prevention n of problems problems in subsequent subsequent process process steps steps

Fachforum parts2clean 2012

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SurTec SurT ec Deutschland GmbH

Which Types of Corrosion Protection are Known? 

Active corrosion protection

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Passive corrosion protection

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Temporary corrosion protection

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Aqueous temporary corrosion protection

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Oil emulsive corrosion protection (wax, grease, emulsion)

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Vapor-Phase-Inhibitors, VCI (volatile corrosion inhibitor)


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SurTec Deutschland GmbH

Active Corrosion Protection Material Selection 

Simple but often not manageable method due to potential technical or economical factors

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Resistant materials are often very expensive

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Required mechanical characteristics are not given very often


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Active Corrosion Protection Corrosion Preventive Planning and Constructing 

Avoid gaps, joints, angles, edges and rough surfaces

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Avoid contact elements (direct contact of different metalls)

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Quick removal of swarfs and metall abrasion (possible induction of corrosion also under the protected layer)

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Effective extraction ans neutralisation of aggressive medium (acid vapor)

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Separation of ferrous- and non-ferrous metals during fabrication

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Most short storage time between the process steps

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Quick drying respectively cleaning after a treatment with corrosive media, especially in accordance with gabs, pores and stud holes


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Active Corrosion Protection Storage- and Transport Conditions

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Choose adequate packaging means (air- and waterproof) optionally usage of VCI-paper or VCI-foil

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Preferably constant and low temperature and humidity

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Avoid contact with aggressive media (salts, perspiration, emissions or condensate)

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Downward storage of pores and notches, so water can drain and the creation of corrosion cavity will be avoided

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Adequate ventilation of the parts (avoid condensation water)


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Active Corrosion Protection Impact of the corrosion medium

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Drying of air, blast and gas

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Desalination of the used water (usage of deionised water) to avoid chloride- and sulphate enrichment

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Inhibit aqueous processing media (KSS, cleaners, ...) with anorganic or organic inhibitors

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Inhibit other media (oil, lubricants) with e.g. amines or fatty acid derivatives

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Inhibit acidic pickling (suppression metall removal and und minimisation of hydrogen embrittlement)


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Passive Corrosion Protection Passive corrosion protection = Application of a separation layer For iron and steel generally: 

Metallic coating (zink, nickel, zinc alloy), electroplating processes

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Organic coatings (lacquer, paint coat), e.g. Golden Gate Bridge

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Non-metallic coatings (enamelling, blacking, gas nitriding)


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Passive Corrosion Protection Phosphating 

Apllying an iron-, zinc- or mangan phosphate layer in dip- or spray coating process

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One-step-procedure (cleaning + phosphating) possible

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The corrosion protection should be increased by a subsequent oiling

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Acts as an improvement of the material characteristic in the production process, e.g. cold forming or as primer for painting not as pure corrosion protection


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Temporary Corrosion Protection 

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Normally, a temporary corrosion protection is a passive corrosion protection which can be added to the active corrosion protection due to the usage of VCIPaper or by usage in cleaning- or rinsings baths It is the aim to achieve an adequate corrosion protection on the parts during production process, storage and transportation Aqueous and oil emulsive mediums belong to temporary corrosion protection The maximum length of corrosion protection adds up to approx. 2 years, depending on the application. The resistance is hooked on the environmental conditions and increases clearly in comparison from the aqueous to the oil emulsive mediums. The removal of oil emulsive corrosion protection medium is more difficult than the aqueous medium


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Aqueous Temporary Corrosion Protection 

Normally adducts of fatty acids an amines

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Produces a mild alkaline to alkaline setting on the surface of the parts

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Are salt-free and thus adequate mixed substrates

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Form a dense film on the surface of the part

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Can (depending on the chain lenght) create a hydrophobic film, e.g. SurTec 104

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Hydrophobic films can disturb the subsequent lacquer processes and can only be removed alkaline


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Aqueous Temporary Corrosion Protection 

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Is added in the rinsing baths respectively the last rinse (0.5 – 1.0 Vol%) Corrosion sensitive parts or cleaning (mildly alkaline) of e.g. aluminium or steel, products will be added to the cleaning bath which contain an temporary corrosion protection to protect the ironmetals These corrosion protection films are dried up on the surface Subsequent processes like tempering will not be effected negatively, as the corrosion protection are completely vaporized by temperatures above 200 °C Depending on material and storage conditions or water quality a corrosion protection times from 2 weeks to 6 months can be achieved


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Aqueous Temporary Corrosion Protection Requirements for a good aqueous temporary corrosion protection: 

Make-Up in deionised water

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Water quality from < 10 mg/l chloride and < 20 mg/l sulfate

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Qucik and total drying after cleaning or passivation

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Vacuum drying is beneficial for parts with a complex geometry

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The parts need to wrapped in corrosion protection paper when dry and cooled down

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Parts which will be forwarded to assembling need to be stored dry and in a dry environment

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Regular control of the cleaning- and rinsing baths on chloride- and sulfatecontent


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SurTec Products with Temporary Corrosion Protection Cleaner with temporary corrosion protection: For iron + steel: 

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SurTec 108 -> phosphate-containing, tenside-free, pH: 10 SurTec 042 -> salt-free, tenside-containing, pH: 10 SurTec 531 -> salt- and tenside-free, pH: 12

For iron + aluminium:

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SurTec 001 -> salt-free, tenside-containing, pH: 8 SurTec 010 -> salt-free, tenside- and biocide-containing, pH: 8 SurTec 101 -> salt-free, tenside-containing, pH: 8 SurTec 102 SFT -> salt-free, tenside-containing, pH: 9 SurTec 104 -> salt-free, produces a hydrophobic film, pH: 8 SurTec 107 -> phosphate-containing, tenside-free, pH: 8

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SurTec 107 and SurTec 108 should not be used in rinsing baths due to their saltiness

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SurTec Products with Temporary Corrosion Protection Corrosion protection for rinsing baths: For iron + steel 

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SurTec 531 SurTec 533

Für iron + aluminium 

SurTec 534

Corrosion protection times: 

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Aluminium -> 1 week up to 3 months Steel -> 2 weeks up to 6 months Requirements are a good water quality as well as bath control and dry storage of the parts


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Analysis of the Corrosion Protection Baths 

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Method for determination of the concentration of the corrosion protection via acid-base-titration. Analysing the chloride- and sulfate-concentration in the corrosion protection baths. Another method to determine the corrosion protection in the bath is a DIN Eine weitere Methode zur Bestimmung der Korrosionsschutzleistung im Bad ist der DIN-Späne-Test according to DIN 51 360 part 2. Here, the corrosion protection of the bath ist tested with grey iron swarfs. The results will be compared with a chart and the respective corrosion category will be assigned. Corrosion category 0 = no corrosion Corrosion category 1 = traces of corrosion Corrosion category = light corrosion Corrosion category = moderate corrosion Corrosion category = high corrosion 

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Oil Emulsive Corrosion Protection Corrosion Protection Emulsions: 

Aqueous emulsions of mineral oils and wax

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A dry to handle surface can be achieved after drying

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Contain inhibitors, that prevent that the aqueous phase leads to a metal corrosion

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Solvent-free application

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Corrosion protection value of wax can be achieved

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Product from the SurTec-Range: SurTec 590


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Oil Emulsive Corrosion Protection Corrosion Protection Oils: 

Mineral oil raffinates

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Produce viscouse films on the surface of the part

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The protective effect depends on the viscosity of the oil

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Often oil soluble amines (< 1%) are added to improve this protective effect Are apllied either undiluted or as fluid (diluted with benzine)


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Oil Emulsive Corrosion Protection Corrosion Protection Fat: 

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Vaselines packed with inhibitors Are applied obviously thicker as oils (layer thickness: 500 µm) Are often thickend with metal soaps to increase the drop point

Corrosion Protection Wax: 

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Complex, liquid systems of wax or waxen substances Contains white spirit and corrosion inhibiting substances (e.g. silicon oils) Produce dry-to-handle ductile-hard layers Bee wax, hard paraffines or lanolin are used as coat former


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Vapor-Phase-Inhibitors 

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Cost-effective alternative for longer storage and transport Consist of Bestehen aus volatile powders or liquids which are used in form of paper, foil, packages or pellets Impacts by corrosion lock on the metal surface They evaporate until the vapor pressure is leveller and condensate on the metal surface

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After usage of the VCI the corrosion protection effect disappears

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Only for use in closed trading unit


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Summary 

The corrosion residence of the parts depends on many factors, and is usually in direct correlation with the resulting costs.

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Therefor regular economic analyzes should be carried out.

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Aim should be to optimize all characteristics.

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The main characteristics are: 

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surface appearance (avoid of rough surfaces, quick cleaning and preventing of salt residue) short storage time and route of transport under optimal conditions preferably corrosion-resistant materials Avoiding aggresive media (acid fumes, condensate, swarf, abrasion)


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Conclusion 

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It can be seen that an influence on the corrosion protection of the parts does not begin until after a cleaning process, but during the design of the parts. In order to achieve a sufficient corrosion protection over a given period it is important to consider the entire manufactoring process up to the transport. Thus any problems can be detected and avoided promptly. In this way complaints regarding corroted parts can be minimized or maybe even completly avoided.


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Danke!

SurTec International GmbH

www.SurTec.com

SurTecCorrosion Protectionparts2clean Forum.2012

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