| Re: Flushing afterwards |
Subject: Re: Flushing afterwards by CentralCoaster on 2008/3/21 21:28:05 There's 3 different things going on here, don't confuse them. RUST - oxygenated water corroding metals GALVANIC CORROSION - dissimilar metals in contact in water) ACIDIC WATER - pure water dissolving metals RUST occurs extremely slow in 100% pure water because of its extremely low conductivity and lack of free oxygen. The pure water molecules must be reduced down to H2+ and O3- before the iron can oxidize, and these reactions need electrical conductivity to occur. In tap water, you have dissolved oxygen ions which readily corrodes the iron. You also have dissolved hydroxides and dissolved metals in there, like sodium, calcium, magnesium that increase its conductivity, which speeds up the corrosion process. The steel and cast iron will corrode much faster than aluminum. GALVANIC CORROSION. The high conductivity increases the rate of galvanic corrosion, ONLY IF there are dissimilar metals in direct contact with each other and the electrolyte (coolant). This occurs where the alum heads meet the iron block, or where the iron heads meet the alum intake, depending on year. The contact is made through the head gasket and bolts, or at the intake through just the bolts. (If the intake bolts on a 84-85 car were insulated from the intake with plastic sleeves, no galvanic corrosion would occur there.) ACIDIC WATER, mostly distilled water, has a low pH and will slowly dissolve almost anything it touches until the pH becomes neutral. This is why it's usually stored in plastic or glass or tin. |
