Corrosion classification 2

[Steved]

Good morning:<br>
<br>
Is there a colormetric or spectrophotometric method or equipment to classify corrosion? We have steel parts that have been coated with electrolytic zinc. Some parts have white corrosion, some have rust. We would like to classify the corrosion and lack of corrosion my color, if possible. I appreciate any suggestions. Thank you and have a great day.<br>
<br>
Steve d

 

[Grapes]

I worked for a company that used a rust inhibitor called galvafroid on any of it's steel parts because those parts were then going to be bolted to aluminum skylight frames. I know exactly what you mean, because when the galvafroid coating was a little thin, iron oxide would peek through the coating after a period of time. I don't know how you would go about classifying the two types of oxidization that are going to be present in that sort of a situation but, the red corrosion you see is iron oxide, and the white corrosion you see is zinc oxide(?). I'm not sure if zinc oxide is the exact terminology for that but I hope it helps.

 

[Steved]

Hi Grapes:<br>
<br>
Thanks for the reply. Have a great day.<br>
Steve d

 

[rustbuster]

Grapes is correct in describing the corrosion products.<br>Regards

 

[Steved]

Hello Rustbuster:<br><br>I thank you for the reply. Take care,<br>Steve d

 

[chlee1]

Zn will sacrificially protect steel, if zn plating is not protected by extra lacquer or paint, easily you may see powdery white (Zn Oxide) and black (Zn Carbonate) corrosion products. For most of the ppl, this considered failure, but for platers, this nature phenomenon.

Generally there are 8 types of corrosion out there (SCC, MIC, EIC, fatigue, H2 Embrittlement etc etc). I'm not sure you were saying to classify all these corrosion types or just distinguish between the Zn rust and steel rust? If the latter you meant, simplest and fastest -- visual + concentrate + little experience.

Hope this helps

 

[Steved]

Hello Chlee1:

Thank you for the reply and the information. Please have a great week.
Steved

 

[robo123]

Hello,
I have some comment on the finish after the Zinc plating.
Basically any plating process finish depends on the finish of the part before plating also. For the first problem of white marks the major reason would be.
>Either the finish is rough- ground finish is preferable.
>Or the part is stripped and replated for some reason. This sould be avoided.

Second problem if the part is getting rusted, please ensure that the plating thickness is minimum of 5 microns for a normal usage. This can be checked using a plating thickness tester.

 

[Steved]

rob123:

Thank you,
steved