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Machine OEM needs help with corrosion

Machine OEM needs help with corrosion

Machine OEM needs help with corrosion

(OP)
My company builds machines for processing granite countertops.  We are experts in machine design and not corrosion.  I'm trying to establish a water specification so our customers don't accidentally cause excessive corrosion.  I'm familiar with the Ryznar index but don't claim to be very keen with it.  The machines operate in a very wet environment (like a car wash) with only water - no additives.  We use very good paint.  In some isolated cases the machines experience excessive corrosion (maybe 5% of the time).  We build the machines out of painted steel, aluminum, and stainless.  What would be an acceptable pH range to minimize corrosion of these materials?  I've been told 7.8-8.2.  Is that correct?

RE: Machine OEM needs help with corrosion

Can you use additives in the water to reduce corrosion?  For Al, pH between 6 & 8 is a good rule.  For iron, pH of 8 to 10 is a good rule.  Galvanic corrosion is a potential problem for you - how do you connect the stainless steel to the other two materials?

Regards,

Cory

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RE: Machine OEM needs help with corrosion

Doesn't the PH go up to around 10-11 when cutting Granite?

RE: Machine OEM needs help with corrosion

i think that the best way to protect you machine is to use a good coating and make inspetion and maintenace of the coating. it would be necessary to know exactly where the corrosion takes place. And also what you mean with 5% of the time?

S
 

Corrosion Prevention & Corrosion Control
 

RE: Machine OEM needs help with corrosion

(OP)
Thanks for your feedback everyone.  I'll answer the questions you've asked.  CoryPad--we rarely experience any galvanic corrosion.  The stainless parts are bolted to the painted surfaces.  I don't know much about additives but would think they'd be acceptable.  Unclsyd, I don't know what the typical pH values are cutting granite, but I do know in the few cases where we experience the extreme corrosion the pH is between 6-7.  Therefore I would guess that if the pH is often around 10 we wouldn't see the corrosion.  Strider6, we use very high quality paint, but a small percentage of customers (5%) still have excessive corrosion--even on stainless.  My objective is to provide an acceptable range and let the customer work with a local provider to solve the problem.  Based on what you've said it seems as if 7.8-8.2 would work.  What is an acceptable range for stainless?

RE: Machine OEM needs help with corrosion

Stainless is fine with the pH levels we are discussing.  You have to keep chloride ion concentrations low to avoid stainless corrosion.

Regards,

Cory

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RE: Machine OEM needs help with corrosion

(OP)
CoryPad,

You've been very helpful.

Mike

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