Corrosion inside pump cylinders 3

[nilcram]

I have the challenge of eliminating a corrosion problem in a grout pump cylinder. The current cylinder construction is quite basic. Low carbon steel (1012 or 1018) that is machined and heat treated. Heat treat process consists of a gas nitriding type process followed by oil quenching. This process is proprietary to my heat treat vendor. They call "Lindure" process. It is not providing sufficient corrosion resistance this product requires. In fact, the currrent process will allow significant pitting of the cylinder ID if simple tap water is allowed to sit inside the cylinder. Need to find a better, more corrosion resistant process. The cylinder is not subjected to high structrual loads. I simply need a process that gives high surface wear on the ID along with good corrosion resistance to water.

Thanks in advance for your expert opinions.

NILCRAM

 

[Goahead]

Nitriding is not recommended for mild steel. Nitride forming elements like aluminum should be present in the steel to provide some advantage. Oil quenching may be needed for that commercial process but it is ineffectual on mild steel.
As you probably do not need hardness,
maybe that coatings of teflon, Sermetel W (

http://www.sermatech.com/about/history.html)

or Magnaplate (

http://www.magnaplate.com/)

would be more effective.

Regards,

http://www.welding-advisers.com/

 

[edrush]

You might try electroless nickel. Iron is slightly more anodic than nickel (a bad thing), but they are right next to each other on the emf chart. Electroless nickel provides a great wear surface and if you put it on relatively thick it might survive the water environment.

EN is part phosphorus and is available in a limited range of phosphorus content. The phosporous content affects the hardness as does the heat treatement of EN. Hard is good for wear.

 

[Carburize]

Is the grout very abrasive?

 

[swall]

I would suggest hard chrome plating. This will provide wear resistance and corrosion protection. For corrosion protection, you will need to specify crack free chrome and/or a base layer of nickel plating.I would suggest a total plating thickness of .001" minimum. One disadvantage of hard chrome compared to the electroless nickel is that you may need to grind or hone the chrome if you put it on too thick.Hard chrome is significantly harder, however.

 

[edrush]

I believe nickel can get into the low 60's rockwell C scale, but the chrome plating may be more corrosion resistant due to the multiple layers and the fact that chromium is involved. Think about how long a chrome plated bumper will last in a state which salts it's roads. I'd say 8-10 years.

Chrome plating may become much more expensive come February. OSHA is considering reducing the PEL for chromium from 50 ug/cu meter to 1 ug/cu meter and the ruling should be out then. They do actually use chromium in chrome plating don't they?