Methylene chloride and carbon steel

[StoneCold]

We installed a 1" carbon steel sch 40 transfer pipe last year. The pipe was liquid full of methylene chloride for the year but there was no flow. The compatability charts that I had found prior to construction were rated "B" as in adequate but not excellent. We removed some of the pipe today and the inside of the pipe showed some corrosion. It was a brown oxide (FeO3?) but it did not appear to affect the integrety of the pipe. The methylene chloride was dried over molesieves prior to being loaded in the line, so it should have been dry. Use of carbon steel in this application appears to have been a mistake. We have some tanks that are 316L and they appear to be in great shape. Would 304L work in this application? Should a person only use metals that are rated "excellent" based on corrosion charts if you need to keep the material clean?


Thanks

 

[Metalguy]

An old Carpenter SS book I have indicates that while the general corr. rates are very low for 304 & 316, they both can pit and/or get "stress cracks" or SCC.

I think that water may be the key here. Your MC appears very dry, so 304 *should* be OK.

I wouldn't use a material rated less than excellent if product cleanliness is important.