Sunday, February 13, 2011
passivation - Astro Pak Names Ronald Pentecost EH&S Director
Thursday, February 3, 2011
Citric Passivation – Passivation and Derouging of Stainless Steel
Stainless steel doesn’t rust because of a process that leaves a very thin coat of chromium or other corrosion resistant surface. The process is called passivation. Passivation is accomplished by depositing a layer of oxide on the surface of the stainless steel. This layer is only a few nanometers thick and protects the metal from any corrosion. The process may also include the removal of all free iron on the surface to prevent any weak spots for corrosion may develop. Citric passivation uses citric acid to remove free iron. It has been used successfully and is not harmful to the environment or to humans.
Passivation is a precision cleaning of sorts. It is used on very large surfaces to remove very small contaminants. It is also used on very small stainless steel parts to ensure that there will be no corrosion especially in a tough environment. Stents that are used in angiography are finished in this way. It is very important that the stainless steel used for medical purposes like in heart surgery or pins for broken bones can withstand moist and chemically tough environments like the interior of the human body.
Derouging is another similar process to passivation. Roughing is a type of corrosion that is found only on stainless steel. Metal that has experienced this type of corrosion can be corrected. Roughing may occur when there is a high incidence of iron on the surface of the metal. Or it may also be the result of temporary support welding jobs that leave a spot of low chromium when the supports are welded off. The correction must be made chemically. The chemicals will not harm the stainless steel, but do remove the rouge. After the chemical cleaning, the surfaces of the stainless steel are repassivated to protect them from further problems.
The whole process is actually quite safe and is mostly pH neutral and uses chemicals that do not cause harm. To passivate stainless steel is necessary for medical instruments or even for use inside the body. To have iron oxide buildup on stainless steel inside the body could become a big problem. But chemically treated metals inside the body could be a problem too. That, however, is not a problem with passivation. These methods and chemicals are completely safe. Citric passivation is a newer process and has proven even safer than traditional methods.
Wednesday, February 2, 2011
passivation – Pigging Your Pipes
When there is a need for deep chemical cleaning, there are various processes that one can use. However, it is important to ensure that you are properly trained before performing any of the following techniques. When cleaning with chemicals, there are multiple risks involved. On the other hand, when it is done properly, there will be a nice clean surface that will not need to be replaced due to grime and build up. Let’s take a look at a few different ways to clean with chemicals that will successfully renew the area being cleaned.
Passivation is a treatment that is used to dissolve iron that has built up on the surface of machinery. If the iron is not removed, the machinery will look like it is rusty due to corroding. This treatment is done by submerging the components into citric acid or nitric acid. If done correctly and without the use of oxidizing salts, the iron will successfully dissolve. Also, an oxide film that is transparent will form on the surface to protect it from any more iron build up.
Passivation of stainless steel will not work if it has a nitride surface or carbonized surface. This is because the component’s size will be reduced when the nitric acid dissolves the surface. When you are finding a company to complete passivation for you, it is highly important to let them know the exact type of stainless steel that you need cleaned. Once your product is successfully cleaned, there will be a new sheen to it and if it is done properly there will not be a reason to have it cleaned again for quite some time.
When talking about cleaning metal with chemicals, one might be interested in knowing more about pipeline pigging. This is the process in which a pipeline inspection gauge (pig) is used to clean the pipes without stopping the flow of fluids through the pipe. When the pig is placed into the funnel at the end of the pipe, the pipe is closed off. Once the pipe is closed, the pressure of the liquid running through the pipe will push the pig all the way through the piping until it reaches the end and all of the gunk will come along with it. This is a very effective way to clean out piping and will not stop the flow of what is coming through the pipe. This way, daily occurrences will not be disrupted.