OSPHO to clean zincs

[hpeer]

Good idea or bad? The OSPHO sure is active and seems to be “cleaning” the white crud off. Am I also screwing with the zincs?

[Steve Bean]

Wouldn't hydrochloric acid (muriatic acid) work just as well and probably be cheaper? Also, ospho literature describes ospho as "a coating." Might this interfere with zinc function?

[Calif.Ted]

I replace them with shiny new ones every 9-12 months.

[hpeer]

Mine are only 8 years old and still pretty hefty. Trying to get another year out of them.

Muratic acid might be better/cheaper but they don’t carry it in the store at the marina in Grenada.

About the “coating” I think that is something different but was hoping to turn over a chemist and see what crawls out.

[Crusty Joker]

You are cleaning a sacrificial metal, ZINC, with a very strong electrolyte. Why do that?
Clean off the contact metal to metal surfaces so there is good electrical contact and fasten the zinc back on to the boat. For that use sand paper or emery cloth, clean the fasteners and washers if any, and put the zinc back on the boat. Zinc does not need to be shiny. Zinc oxide is a white color if I remember my basic chemistry. This is not rocket science. You want to link all metals on the boat to your bonding system. Then all can be protected with a single zinc. Look up Robert Shorey and Torrey Bartel. They taught me how to do this and the reasons a simple system to regulate the current flow to the zinc works well to protect the metals from corrosion from salt water.

[evm1024]

Reacting Zinc with phosphoric acid will give you Zinc phosphate. Zinc Phosphate is not soluble in water and MAY coat your zinc and reduce their effectiveness. I say MAY because I do not know how well the Zinc Phosphate will attach to the parent zinc.

3Zn (s) + 2H3PO4(aq) = Zn3 (PO4)2(aq) + 3H2(g)

I do use OSPHO in cleaning my teak and other woods.

Teka part A is based on Sodium Hydroxide and you can just take some Lye granules and mix them with water to form the part A. Then use OSPHO as the part B. Much less expensive than Teka.

Of course you do need to get the concentration of NaOH correct - I have used Zeps Purple industrial cleaner diluted 1:1 with water for part A (this gives the right molarity of NaOH) and OSPHO at full strength.

[Crusty Joker]

Use sandpaper and fasten the zinc to metal and test resistance. Watch the zinc go to work after you put the boat in the water. Why would you want to go against protecting the metal on the boat and sacrificing the zinc. The zinc is there to be sacrificed.

[dochip]

Ospho is phosphoric acid. I have used it for years in restoring vehicles.
When it is exposed to iron oxide (rust) it chemically changes it to iron phospate, which is inert and therefore stops the rust.


What it's doing with your zincs is beyond my basic chemistry. Zincs are made of zinc, or magnesium and aluminum, so ...


As to using zincs for years, is your boat on a lift or in fresh water? in SW Florida marinas zincs might last 9-10 months.

[hpeer]

Salt water, Carribean. The zincs last a long time, there is plenty of metal left but they are pretty covered with white crud, which seems to be discoloring off.

Heading to our little shop to see about replacements. Supposed to launch tomorrow.

44’ steel boat, 6 rather large zincs.

[Squanderbucks]

Zincs are self cleaning. Unless you get paint on them the y work by corroding instead of the other metals of your boat. They are not supposed to be pretty. If you don't like the way they look just hit them with a wire brush and when they go back in the water they will go back to corroding just like they are supposed to. In the water the "white stuff" washes away by water and wave action to replenish the active surface. Normally just left alone until they are nearly gone - or at least small enough to not last until the nest haul out.

[hpeer]

That’s interesting, previously I’ve heard folks claim the “white stuff” needs to be removed for the zinc to work.

[hpeer]

Originally Posted by evm1024

Reacting Zinc with phosphoric acid will give you Zinc phosphate. Zinc Phosphate is not soluble in water and MAY coat your zinc and reduce their effectiveness. I say MAY because I do not know how well the Zinc Phosphate will attach to the parent zinc..

So I took a piece that had clean up pretty well. It looked like zinc with a slightly dark color. I hit it with a wire brush and it brightened right up. So I’m assuming I’m knocking off the zinc phosphate.

Still not sure if there is any benefit to this process or not. The white stuff/zinc oxide was pretty thick. Opposing opinions about whether or not it adversely effects your protection.

[alaskaflyfish]

Why not use vinegar, it's cheap, effective, and environmentally friendly. I flush my raw water cooled engine with vinegar at the end of every season to remove salt deposits and my internal engine zincs come out perfectly clean. It cleans the thermostat too, makes it look brand new.

[hpeer]

Thought of vinegar, maybe next time. Store had Ospho but not vinegar.

[boatpoker]

Yes, zinc hydroxide or a calcareous coating will insulate the zinc and inhibit it's effectiveness. You cannot be sure just by looking at it. I've seen new zincs with no continuity between themselves and the metal they are to protect.
Check resistance, it should be well below 1.0ohm, preferably 0.0ohm