Your fingernails won’t be the only signs of these diseases, but they can provide confirmation or motivation to seek medical care.
Stainless steels are corrosion resistant because an oxide film, rich in chromium and nickel, completely covers the surface. The low alloy steels that contain around 8% alloying elements are ferritic or martensitic and have good mechanical properties.
Corrosion resistant grades of martensitic stainless steel are generally referred to as the 400 series. As the alloy content is increased, mainly by the addition of nickel as an alloying element, the steels become more austenitic and non-magnetic.
Common grades of austenitic stainless steel are 301, 303, 304, 316, 317, 321, 314 (in increasing alloy content). Grade 301contains slightly less chromium (16-18%) & less nickel (6-8%) than grade 304 although the two grades can overlap with a good quality grade 301 being equivalent to a poor quality grade 304.
Grades 321 and 347 stainless steel are modifications to grade 304 to which titanium or niobium have been added to desensitize the material from carbide precipitation which results in inter granular corrosion and occurs as a result of heating the material during welding.
Grade 316 stainless-steel is the most corrosion resistant of the commonly found stainless steel grades. Duplex stainless steels generally contain between 19 and 24% chromium and between 3 and 5 per cent nickel. Crevice corrosion is the second most common mode of failure of stainless steels, with pitting corrosion being the most common. Crevice corrosion occurs at locations where there is a small gap, or crevice, between the stainless steel article and another item.
The mechanism of crevice corrosion is well-known, with the first stage being the accumulation of aggressive ions (such as chloride ions) in the gap and the exclusion of oxygen from the solution within the gap. Good design is one of the best ways to avoid crevice corrosion, with materials selection coming a close second. Other passive materials such as aluminium and its alloys are susceptible to both crevice corrosion and pitting corrosion.
The most usual type of localised corrosion attack on stainless steel which results in perforation of tanks, vessels and pipe walls is pitting corrosion. The pits are the anodes in the corrosion reaction and the remainder of the surface is the cathode. The conditions that lead to pitting are moderately high temperatures, high concentrations of chloride ions (from salt), other halides such as fluorides, bromides and iodides. This acidity within the pit is the reason why pits can continue to grow once they have been initiated.
Each stainless steel alloy has a critical pitting temperature, above which pitting can be expected to initiate and propagate. The most common austenitic grades of stainless steel will, therefore, be above the critical pitting temperature under many common service applications.
For critical application, where pitting corrosion is to be expected, it is common practice to carry out passivation treatments in an attempt to bring the metal surface to a more uniform condition. This is carried out by treating the surface with oxidising acids that dissolve iron but not the oxides of the alloying elements. The rate of both the nitric acid and citric acid passivation processes can be increased by raising the temperature.
ASTM standards are a guideline only, as the passivation treatment chemicals, process conditions and time have to be matched to both the operating conditions and the corrosive environment. Tests for the effectiveness of the passivation treatment can be electro-chemical, using polarisation curves and potential mapping, or chemical, using either copper sulphate or ferricyanide tests. Polarisation curves on stainless steel are carried out using a potentiostat that holds the voltage constant and measures the resulting current. Polarization curves plot potential on the vertical axis (in mV with respect to the type of reference electrode) and the log modulus of the current along the horizontal axis. The sharp peak of low current pointing leftwards on the graphs, occurs when the current goes through zero.
The curves are often carried out starting from the bottom of the graph (electronegative) and sweeping towards the top (electropositive). Where the positive part of the curve is vertical, or nearly vertical, this is a passive area where a high resistance, voltage independent, thin chromium film is present on the surface. A second measurement of the corrosion current can be obtained by extrapolating the electronegative (cathodic) part of the curve back to the zero current potential. Sensitization of stainless steel is a form of intergranular corrosion or grain boundary attack which results in complete grains of material falling out from the surface of the metal in the manner shown in the above photograph.
Sensitisation results in corrosion as the grain boundaries become depleted in chromium due to the formation along the grain boundary of intermetallic carbides. When stainless steel has to stay in a good visual condition it should not be assumed that it will be maintanence free. Stainless steel is commonly used externally in modern buildings because of its attractive surface & low maintanence requirements. The photo above shows how a poor cleaning regime can lead to corrosion in an industrial kitchen. Kitchen stainless steel surfaces can corrode rapidly if the equipment is supplied in a poor condition. The severe pitting and corrosion shown above is an extreme case where a chlorine containing cleaner has caused corrosion of an industrial sink unit. Many pharmaceutical plants process saline solutions & are constructed from type 316L stainless steel. The photograph above shows the blackening that occurs on type 316L stainless steel on a vessel that was regulary carrying acids. The photo above shows a stainles steel spray nozzle from a dairy that is corroding from the inside out. Food processing conveyors such as that shown above can rapidly corrode if supplied in an incorrect surface condition.
Stainless steel hand rails are common in swimming pools and are generally resistant to corrosion from the pool chemicals. Vein walls are composed of the same three layers as an artery but the media layer is much thinner. Venous valves normally allow flow to move in one direction in the vessel, toward the heart.
Note the size difference between the two extremities which can be a sign of acute DVT, if it has an acute onset. Normal venous response to the Valsalva maneuver is cessation of venous flow toward the heart.Flow reversal upon release of the Valsalva maneuver indicates the presence of reflux. If flow reversal occurs at the onset of the Valsalva, the duration of the reflux flow must be measured. The distal augmentation maneuver is used to confirm the absence of DVT following the compression maneuvers.
Pitted scars, also known as boxcar scars, pockmarks and ice-pick scars, represent the most common type of acne scar. Over-the-counter treatments can make shallow, saucer-shaped acne scars appear less prominent. Other options for treating pitted acne scars involve procedures that strip off the top layer of skin, making the deepest pits appear shallower and potentially removing any shallow pits. Surgery and other physical procedures used to treat deep acne scars and pitting require significant recovery time, and you likely won't see immediate improvement in your scars, the Academy of Dermatology warns.
Acne scars often are difficult to treat, and the Mayo Clinic says no one treatment works for everyone.
Thickening nails are a change that should tune you in to other health symptoms you may be ignoring. Watch what you eat and check the psoriasis connection to fight back and pay more attention to your health overall. Your fingernail and health challenges go hand in hand – for many people, clearing up their health issue results in their spoon nails returning back to normal. Small dips or holes in your nails can be a result of banging up your hands – or they could be a sign that you need to look more closely at your health.

Both thyroid and fungal issues take time to treat, so you won’t see a difference in the look of your fingernails for a full growth cycle.
If you have plump skin that seems to swell around the nail, or if your nails seem to have puffed around your fingers, they are said to be “clubbed”. Your fingernails won’t be the only signs of these diseases, but they can provide confirmation or motivation to seek medical care.
Your fingernails won’t be the only signs of these diseases, but they can provide confirmation or motivation to seek medical care.Don’t ignore your hands or the health warnings they send.
Your fingernails can give you valuable health warnings and signal the presence of serious disease.
Discolored nails - A healthy fingernail should be pink with a touch of pinkish white (moons) near the base.
Pitted nails - Small dips or holes in your nails can be a result of banging up your hands – or they could be a sign that you need to look more closely at your health.
This Guide is one of a series on our website dealing with a number of Corrosion & Coating Breakdown topics. Steels containing less than 8% alloying elements have very similar corrosion rates to normal mild steel. Grades with numbers between 403 and 420 generally contain between 11% and 14% chromium, the more corrosion resistant grades with numbers between 430 and 440 contain between 15% and 18% chromium. Higher alloying contents lead to improved corrosion resistance, especially to pitting and crevice corrosion. However the strength of the steel increases and some of the cost penalty can be regained by using reduced cross sectional areas and thicknesses. Where only low levels of corrosion resistance are required grade 3CR12 could be considered as a low cost option (non austenitic option) if some degree of pitting and general rust staining is acceptable.
Depending on the amount of cold work grade 301 can be differentiated from grade 301 due to it being mildly magnetic.
It contains between 16 and 18.5% chromium, between 10 and 14% nickel, and between 2 and 3% molybdenum. It has excellent corrosion resistance without having the welding problems of duplex grades. Duplex stainless steels have microstructures that consist of a mixture of austenitic and ferritic phases. This second item can commonly be an insulator such as a gasket or a rubber separator although it could be metallic.
This results in a fixed anode forming in the crevice with the material outside of the crevice becoming a fixed cathode.
Crevice corrosion is most severe in acid conditions in chloride containing, non flowing or stagnant environments. Pitting and crevice corrosion of aluminium occurs by similar mechanisms to that of stainless steel. Alloys that have high concentrations of nitrogen (N), chromium (Cr) and Molybdenum (Mo) have been found to show good resistance to pitting.
However, passivation treatments and control of the surface finish can be used to minimise the effect of adverse service conditions. ASTM A967-1 gives citric acid at 8% for 3 hours at room temperature as a common treatment and it is relatively safe to handle. Passivation times can vary from a few minutes to several days, depending upon the grade of stainless steel to be treated. The electrochemical polarization and potential mapping techniques are far superior, providing more information and better accuracy. These are electrochemical measurements carried out in the solution of interest using three electrodes: the material under test, a voltage reference electrode and a third electrode from which the polarizing current flows.
The modulus is used so that the positive and negative curves appear in the same quadrant on the graph. At the highest voltage, the sweep can be immediately reversed and the voltage returned to the negative starting point, at the same rate.
This causes the shift in rest potentials and sometimes results in a lag in the curves after the reversal point. The voltage range over which this film is stable is an indication of the quality of the passive film. Six carbon atoms take 23 chromium atoms out of the alloy.This can result in the chromium content being reduded from 18 % down to 12% locally.
If the steel comes into contact with non-stainless or ferritic steel then these can smear across the surface and cause local anodes.
The photo above shows a milled surface but brushed, ground & polished surfaces are also common. In urban or marine situations regular washing with warm water containing surfactants will be required to keep the surface in good cosmetic condition. Corrosion such as that shown in the above photograph can take place if the stainless steel comes into contact with building rubble or ferritic steel during construction. Components such as stainless steel shelving or stainless steel work surfaces tend to be constructed from lesser grades than 316 as they are more easily formable.
An example of poor manufacturing is shown in the above photograph where the contrast between the two different surface manufacturing conditions is apparent. Milder forms of this type of corrosion occur when the wrong type of cleaner or bleach is left in contact with stainless steel. Generally the stainless steel performs well, however if clamped flanges are left in contact with saline solutions the type of crevice corrosion shown in the photograph above can occur.
Such staining is a common feature of chemical tankers & is often associated with a degree of surface roughening.
Often dairy or other food products contain salt & if they are left in long term contact with stainless steel then corrosion can occur. This surface had been bead blasted, similar brushed surfaces in the same plant remained in good condition.
The flow will increase toward the heart with distal augmentation but will reverse in direction after the initial increase. The American Academy of Dermatology says some 85 percent of teens suffer from some pimples. Dermatologists aren't certain why some people develop scars, but family history and genetics appear to play a large role, as does acne severity--if you have severe cystic acne, you're much more likely to develop pitted scars. Dermatologists use laser beams, dermabrasion tools and strong acid chemical peels to remove this layer of skin; the treatments have the advantage of diminishing wrinkles and making the new skin appear younger, as well.
Side effects from the procedures vary, but most cause visible wounds, which you'll need to treat at home. It's impossible to completely erase pitted acne scars, although treatments work well to minimize them. Many serious health issues along with serious problems in lungs, liver and heart can be seen and detected early through your fingernails. If your nails are a dull color or streaked with other colors, you may have a serious hidden health problem. Given the “rainbow” of potential health challenges, you want to be sure you see what your fingers are saying. You want your nails to be strong, but if they resemble talons or claws more than traditional nails watch out!
Also watch out for allergic reactions to new medications which can show up as suddenly thick nails! To be considered full spoons, nails will be soft and curve up, forming a dip that is often big enough to hold water.
If your nails are dry and brittle, you should check your hormone levels and bacterial health. Fingernails and disease are more closely related than you think – check your nails often to protect your health! Nail pitting can signal: -Psoriasis -Connective tissue disorder -Alopecia areata, an autoimmune disorder that causes hair loss -Zinc deficiency (when the pit seems to form a line across the middle of your nail) Watch your hand to separate natural dents and dings from real, lasting pits. If your nails are dry and brittle, you should check your hormone levels and bacterial health.

Fingernails and disease are more closely related than you think – check your nails often to protect your health! Other pages are focused on areas such as marine corrosion, Industrial corrosion, Corrosion in Hot Water & heating Systems.
They should be regarded as low corrosion steel rather than stainless as they tend to pit and surface stain. The advantage of this grade is that it can be easily deep drawn into shapes such as sinks and saucepans together with other highly formed industrial articles. It is the material of choice where high levels of pitting and crevice corrosion resistance are required in chloride containing environments. Because of this they have properties that are very similar to both ferritic and austenitic stainless steel.
Corrosion occurs within the crevice for two reasons, firstly a passive film breaks down due to the exclusion of oxygen and secondly the corrosion reactions at the anodic site produce a change in the pH which means that the crevice becomes increasingly more acidic with time.
Cathodic protection can reduce the levels of both pitting corrosion and crevice corrosion by making the anodic area more alkaline. These are usually less than 1mm in diameter and can penetrate many millimeters into the metal. Commonly, these defects are inclusions that form from impurities, such as sulphur, in the steel. Amtec consultants and corrosion experts are specialists in both types of passivation testing and interpretation of the resulting data. A second zero current potential often occurs, followed by a more extensive cathodic region.
The projection of this line down to the X (current) axis shows the corrosion current that could be expected when the film is present on the surface. Where the sensitisation is related to a band across the component it is called Knife-line attack, as historically a heated band close to the handle of the stainless steel knife tended to lose hole grains fromm the surface which left a blackened pit. When sensitised stainless steels encounter a corrosive environment, the centre of the grain becomes a cathode & the grain boundary becomes a very active local anode site. Usually the choice of stainless steel surface finish is a cosmetic one made by architects or designers but consideration should also be given to corrosion resistance issues.
A typical wasing interval will be in the order of six months, however in more severe conditions more regular washing will be required. Similar surface stains can easily occur due to a poor cleaning regime when the building is in a marine or industrial environment. As sterile surfaces in meat processing are essential, often chloride containing cleaners have to be used. When stainlesss steel components or signs are specified for internal use in swimming pools then regular cleaning & washing would be expected. Acne scars can be difficult to treat, but dermatologists offer an array of treatments for pitted acne scars.
Grade 630 does contain between 3 and 5% nickel and between 3 and 5% chromium, these additions results in this material being precipitation hardening and just machinable. Passivation treatments can be used to remove any residual iron from the surface and make the surface film much more uniform and resistant to localised corrosion.
Grade 301L has a low carbon content for better ductility whereas 301LN is a low nitrogen variant which work hardens more easily.
It has excellent corrosion resistance in many atmospheric corrosion environments, however it is quite susceptible to pitting and crevice corrosion in warm chloride containing environments and as such its use should be avoided in Marine applications or applications in the food industry where chloride containing cleaning agents are employed. It is chosen for its good surface appearance in the architectural and transportation areas, however exposure to warm chloride containing environments can still result in unsightly rust staining and cosmetically undesirable small pits. They are extremely corrosion resistant and have a high degree of resistance to both pitting corrosion and crevice corrosion.
The gap has to be just big enough to allow an aggressive liquid to penetrate into the gap but not big enough to allow material to be flushed out of the gap due to flow or convection in the fluid.
Arranging for the environment to have greater flow will also cut down the effects of both forms of localised corrosion.
These impurities can result in very local depletion of the alloying elements, thereby preventing the protective oxide from being totally uniform. 2% sodium dichromate can also be added to the nitric acid treatment to improve the passivation, however there are greater health and safety issues. For 316 stainless steel sensitisation can occur when the steel is heated to a temperature between 480 deg C and about 900 deg C. The process can have a long initiation period as it can take quite a time for the surface grains to become undermined.
In general the smoother the surface condition, the more resistant the stainless steel surface is to corrosion & rust staining. Cleaners containing active ingredients such as ammonia or chlorides should be strictly avoided. Stainless steel in pharmaceutical situations can also be subject to pitting if insufficient flow is present in the process fluid. Stainless steel heating pipes in product carriers regulary carring naptha can suffer pitting corrosion if they are subject to surface damage prior to & during installation.
In this surgical procedure, the dermatologist either cuts out the deep scars or uses a surgical instrument to separate the upper layers of skin from the scar.
If you're considering treatment for your acne scars and pitting, your best bet would be to schedule a consultation with a dermatologist. Further increases in alloying content give rise to duplex stainless steels, which are again more chemically resistant.
It will also have a higher PREN number and better pitting resistance than the standard grade. Hydrofluoric acid can also be used for passivation of stainless steel, but it is a very dangerous process. At the higher temperatures sensitization can initiate after as little as three minutes but at the lower temperatures times of more than 1hour are required.
However when the grains become loose they fall out of the surface as metallic flakes & leave a blacked pitted surface.
Rough surfaces tend to initiate surface pitting in conditions where smoother surfaces would be resistant.
Stagnant solutions may also cause corrosion of stainless steel ball & butterfly valves. Stainless steel doors & air conditioning plant will need regular cleaning and preventative oiling. Once that's complete, the dermatologist may recommend using a filler to finish smoothing out the skin. There are two types of duplex stainless steel known as first-generation and second-generation, the improved second-generation materials contain more nitrogen and have a much better resistance to corrosion by pitting.
In the pharmaceutical industry passivation is sometimes carried out using a very pure solution of phosphoric acid. Sterilising vapours such as peracetic acid used for gassing can also attack stainless steels. Make a note of the color of the nail itself, the skin under it, and the skin around the nail. They are differentiated from super duplex corrosion resistant stainless steels in that they generally have PREN numbers of less than 40 whereas the super duplex material has PREN numbers (see below) of more than 40.
The acids used for passivation treatments should be virtually free of chloride or fluoride ions otherwise pitting of the stainless steel can be initiated. Grades such as 304 or 316 which are only marginally resistant to rust staining in food processing or marine conditions are definitely susceptable when used in a rougher surface condition.
Where speed controlled pumps are used the stainless steel may also be subject to stray current corrosion. These types of steel are known under propriety names such as SAF 2507, Ferralium SD40, & Zeron 100.

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