Category Archives: Uncategorized

Korrosioonitestid ja konsultatsioonid

July 20, 2018Uncategorizedkorrosioon, korrosiooni ennetamine, korrosiooni testid, korrosioonialane nõustamine, korrosioonitestid, korrosioonivormid, rooste, roostetamineCaptain Corrosion

Pakume korrosioonitestide teenust, millega saate hinnata enda materjalide, pinnakatete, valmis toodete või nende komponentide vastupidavust reaalses kasutuskeskkonnas. Katseobjekte pildistatakse ja/või kaalutakse enne ja pärast teste või vajadusel testide vältel. Samuti võime määrata pinnakatete paksust ja selle muutust testide tulemusena. Testide tulemusena saate valida parimad materjalid ja nende kombinatsioonid et tagada tootele võimalikult pikk eluiga ning samuti näidata klientidele et teie tooted on spetsialistide poolt testitud.

Hinnapakkumise saamiseks esita päring lehe lõpus oleva kontaktvormi kaudu.

Keemilised testid

Katseobjekt sukeldatakse ettenähtud ajaks lahusesse, milles ta aja jooksul hävib (korrodeerub). Lahus valitakse vastavalt testitavatele katseobjektidele ja pinnakatetele eesmärgiga simuleerida võimalikult hästi reaalset kasutuskeskkonda. Kergemini korrodeeruvate sulamite puhul kasutatakse näiteks soolalahust, mille abil saab hinnata testitavate objektide käitumist mereäärses piirkonnas. Väga vastupidavate sulamite (nt roostevabade ja happekindlate teraste) omavaheliseks võrdluseks kasutatakse happelisi või leeliselisi lahuseid ning raudkloriidi. Testide pikkus sõltub katseobjektidest ja kasutatavatest lahustest ning on enamasti kuni 1000 h. Keemilised testid on kõige lihtsamad ja odavamad testid, millega tavaliselt korrosiooniuuringuid alustatakse.

Niiskuse testid kliimakambris

Katseobjekt viiakse kambrisse, kus saab tekitada sobiva niiskuse (nt 5-95%) ja temperatuuriga (nt 20-60 C) keskkond. Testi kasutatakse sageli selleks, et saada teada kui suure niiskusega keskkonnas elektroonilist seadet kasutada saab. Ehk siis keskkonnas, kus on niiske õhk aga seade ise otseselt veega kokku ei puutu (sh ka olukorrad kus seade on korpusega kaitstud) ja samuti ei kondenseeru vesi pindadele. Seade tuleb testi ajaks välja lülitada ja vooluvõrgust eemaldada. Samuti tuleb eemaldada ka akud ja patareid. Testid kestavad enamasti 100-1000 h.

Soolaudu testid

Katseobjektid viiakse ettenähtud temperatuuriga (nt 35 C või 60 C) kambrisse, kus tekitatakse soolaudu, mis tagab selle et katseobjektid on pidevalt õhukese soolaveekihiga kaetud. Test viiakse läbi vastavalt ISO 9227 standardile ja tulemused on selle põhjal hästi võrreldavad ka mujal läbiviidud testidega. Võrreldes keemilise testiga, on soolaudu test oluliselt kallim kuid korrosioon kiirem kuna kasutatakse kõrgemaid temperatuure. Soolaudu testid kestavad enamasti 1-1000h. Hind sõltub sellest kas testitakse üksikuid objekte, või broneeritakse testide jaoks kogu kamber, kuhu lähevad vaid ühe kliendi objektid sisse. Hind sõltub seejuures ka objekti suurusest – nt 15 x 15 cm2 plaatide puhul on hind kõige odavam. Kui testitakse aga suuremaid seadmeid, mis võtavad kambris rohkem ruumi, siis sõltub hind sellest mitme plaadi koht seadme poolt hõivatakse.

Elektrokeemilised testid

Kõige kiiremini saab infot materjalide ja pinnakatete vastupidavuse kohta korrodeerivas keskkonnas kui kasutada elektrokeemilisi teste. Ühe objekti testimine võtab seejuures aega kuni 2 tundi, mis võib olla võrreldav tuhandete tundide pikkuse keemilise testiga. Kuna tegu on kiirendatud korrosiooniga, siis võivad tulemused siiski erineda veidi pikaajalistest testidest. Seetõttu sobivad elektrokeemilsied testid olukordadeks, kus on vaja kiiresti leida parim pinnakate või materjal paljude kandidaatide seast. Seejärel viiakse parimate kandidaatidega läbi keemilised testid ja soolaudu testid.

Pinnakatete paksuse määramine ja materjalide uuringud

Materjalide ja pinnakatete korrosioonimehanismi paremaks kirjeldamiseks viiakse sageli läbi täiendavad uuringud. Näiteks mõõdetakse pinnakatete paksust enne ja pärast testi ning määratakse materjalide elemendilist koostist. Samuti on võimalik uurida materjalide mikrostruktuuri, et näha kuidas elemendid on mikroskoopilisel skaalal jaotunud ning kas tegu on kvaliteetse materjaliga või mitte (see omakorda mõjutab korrosioonimehanismi). Pinnakatete täpsema paksuse, mikrostruktuuri ja alusmetalliga nakkuvuse uurimiseks saab teha ka ristlõikeid, mida uuritakse seejärel skaneeriva elektronmikroskoopia ja röntgenmikroanalüüsi meetodil.

Consultation

February 12, 2016UncategorizedCaptain Corrosion

Need advice with corrosion prevention or materials and engineering?

Source: Consultation

How to Generate Hydrogen by Splitting Water

January 6, 2015Uncategorizedalternative, ampere, anode, automobile, car, cathode, chemical, chlorine, clean, corrosion, current, dollar, electric, electricity, electrochemical, electrochemistry, electrolysis, energy, environment, EUR, euro, experiment, experimental, free, fuel, fuel cell, fusion, fusion reactor, gas, generate, generator, global, global warming, green, H, H2, H2O, HHO, how to, hydrogen, hydrogen damage, oxygen, power, reaction, solar, USD, volt, voltage, water, water splittingCaptain Corrosion

Hydrogen is the most abundant substance in the universe. It fuels the starts that light the nightsky. Hydrogen will also power the future of mankind as it is already used as car fuel and within this century even in fusion reactors.

As most of you know, a water molecule consists of one oxygen atom and two hydrogen atoms. So in order to get hydrogen, it is needed to split the water molecule. This can be done for example electrochemically where an electrical potential is applied between electrodes in a salt water. For a home experiment one can simply put a 9 V battery into salt water and watch how hydrogen bubbles start to form at the cathode. At the same time oxygen is generated at the anode but since the anode on the battery is usually made of steel, it will quickly corrode as it reacts with chlorine and oxygen. This causes the salt water to go brown. So instead, you may want to use electrodes instead that are connected to an external power source. If a DC voltage is used then especially the anode needs to be made from a chemically inert conductive material such as platinum which doesnt oxidize. At this anode oxygen gas can be collected. At the same time hydrogen gas is generated at the cathode and can also be collected. If DC voltage is used then the electrode at cathodic potentials will not corrode very quickly as oxidation cannot occur. However hydrogen damage may eventually destroy the electrode.

Hydrogen damage occurs when the small atomic hydrogen generated at the cathode moves into pores and cracks inside the electrode and combines with other hydrogen atom to form molecular hydrogen. The molecular hydrogen however is too large to diffuse through metal and starts building up inside the sealed crack or pore and pressure increases until it splits the material.

In order to produce as much gas as possible, the surface area of electrodes needs to be increased. Make the electrodes rough, multilayered or highly porous for greater surface area.

If AC voltage is used to split water, then corrosion is suppressed and for some time even stainless steel can be used as both electrodes.

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How to Renew Tarnished Silver

June 12, 2014Uncategorizedcoin, corrosion, electrochemistry, hõbe, hõbeda poleerimine, jewelery, korrosioon, materials science, materjaliteadus, polish, renew, renew silver, renew tarnished silver, silver, silver polishing, silverware, tableware, tarnish, tarnished silverCaptain Corrosion

Silver, a valuable metal, has been used long time in making coins, tableware and jewelery. The metal surface however becomes tarnished within a few years and this is caused by corrosion as silver reacts with the surrounding environment.

The surfaces can be easily renewed with stuff available at home – all you need is water, aluminum foil, salt and soda.

Follow these steps to do it yourself:

1. Mix salt and soda into water

2. Wrap the silver price into aluminum foil

3. Put the wrapped silver piece into the solution and wait a few minutes

For a greater effect you might want to boil the water solution as chemical reactions occur faster at higher temperatures.

Why this simple technique works? Silver is usually tarnished as it forms silver sulfide. In order to remove sulfur from the silver, it is needed to put it into contact with a more active metal such as aluminum. The solution there provides with a path for sulfur to move from silver to aluminum.

How Anodizing Works

June 12, 2014Uncategorizedaluminum, anodeerimine, anodizing, corrosion, corrosion protection, electrochemistry, engineering, materials science, materjaliteadus, titaniumCaptain Corrosion

Anodizing is an electrochemical process where a thicker oxide layer is grown on the material. This is useful for improving an objects corrosion and wear resistance, manufacture nanoporous templates or give the material a decorative appearance. Not all materials can be anodized however as their oxides are not dense and hard but the technique has been widely used on aluminum, titanium, zinc, magnesium and their alloys.

The anodizing system consists of a power source, anodizing bath, electrolyte and anodizable material. The bath is usually made from a chemically resistant conductive material such as stainless steel and serves as a cathode. The anodizable material serves as an anode and is placed inside the anodizing bath with the electrolyte. Both the anode and the cathode need to be connected to the power source. The grown oxide layers properties depend on the material, used electrolyte, temperature and electrical parameters used for anodizing.

In order to produce a uniform oxide layer, the substrates are also treated before the process. The main problem is usually organic contamination of the surface, which prevents growth of the oxide layer. This is removed with organic solvents such as acetone. Often the thin native oxide layer is also removed via etching before the anodizing.

How an X-Ray Tube Works

June 12, 2014Uncategorizedbremsstrahlung, characteristic x-rays, engineering, materials science, materjaliteadus, radiation, röntgentoru, security, spectroscopy, tomography, x-ray, x-ray diffraction, x-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, x-ray radiation, x-ray tube, XPS, XRD, XRFCaptain Corrosion

X-ray tubes are widely used for generating X-ray radiation. This radiation has a shorter wavelength than visible light and can easily penetrate through different materials. It can be used in different applications such as materials characterization (XRF, XPS, XRD etc), medicine (x-ray tomography) or security in airports.

The radiation is generated with the help of accelerated electrons. These electrons are first generated on a tungsten cathode via thermoionic emission. Then these electrons are accelerated towards the anode due to a high electric potential between the anode and the cathode. When the electrons interact with the anode, x-rays are emitted. The radiation consists of two components – characteristic x-rays and bremsstrahlung. Characteristic x-rays are generated during the relaxation process of excited anode atoms. This radiation has a specific energy. Bremsstrahlung with a broad range of energy however is emitted from the primary electrons when they slow down or change trajectory during interaction with the anode.

The generated x-rays leave the tube through a beryllium window. This material is used as it has a low atomic number and doesnt absorb much of the emitted radiation.

There are also other types of x-ray tubes, such as the twin anode x-ray tube and the rotating anode x-ray tube.

In the case of twin-anode system, the anodes are made from different materials and only one of them is bombarded with electrons at the same time. This allows fast and easy switching between two excitation energies. The other anode will also serve as a backup if one should fail.

Using a rotating anode allows the heat to distribute on a larger surface area and therefore it is possible to get x-rays with much higher energies and intensities.