Electrical charge developed by a snow plow?

[tjwieseler]

I know this question seems to be a little out there, and I might not be in the right forum, but here it goes.

I have a friend that has a 2008 Ford F350 pickup with a stainless steel Fisher snow plow that has developed a problem with rust spots all over the truck. Rust is even showing up on plastic trim pieces. He previously had a painted steel blade on his truck and never had this problem.

Is it possible that when he is plowing the snow, the snow/dirt/sand/salt (whatever is in the snow) running across the stainless steel might give the truck a positive charge. Then the metal wear bar at the bottom of the blade is wearing off on the concrete and small metal pieces (with a - charge) are being attracted to the + charged truck?

Confused plow owner.

 

[nucleus]

Is your friend using a salt/sand spreader? It could be salt that is causing the problem but we need more information.

 

[tjwieseler]

I know he does spread calcium chloride and possibly magnesium chloride, but this is spread after the plowing is done. I am sure that there is a residual left on the concrete from the last snow fall. I will ask him exactly what he is spreading.

 

[Astronuc]

Seems like old fashioned galvanic reaction called corrosion. The spots on the plastic maybe where solutions of salty water with iron have deposited.

Dissimilar metals in contact will cause the anode (dissolution) to corrode, and stainless steel and carbon steel are sufficiently dissimilar. Chlorides attack stainless steel, which might be a 304, which is one of the most common. If the stainless is more cathodic than carbon steel, the carbon steel may come under attack, and if there are cracks or porosity in the paint, that's where the underlying steel will be attacked.

Also - very importantly - "Large cathode develops current which falls on small anode, producing intense localized corrosion in the form of pitting." Significant pitting can lead to structural or functional failure.

Coatings technology handbook

Principles of corrosion engineering and corrosion control

Physical metallurgy

 

[tjwieseler]

I understand what you are saying about the Galvanic Reaction, but wouldn't that mean that the stainless steel (which is 304) would be the surface that is being attacked, since it is a smaller size than the truck. The rust on the truck looks more like metal flakes deposited on the truck. You can scratch them off with your fingernail. If it was a pit in the paint, I would think you wouldn't be able to scratch off. It is like the truck is attracting the iron filings from the wear bar on the snow plow.