Before diving in deep cycle battery  corrosion we want to define Corrosion process. Corrosion or the oxidation of the deep cycle battery’s grid (where corrosion mostly happens) occurs when  two dissimilar materials in the same electrolyte are connected electronically and  reactions occur at  each material ,result  in causing plate growth and  eventually destroys the deep cycle battery’s grid.
 In our case we take about positive electrode that consist of  active positive material  PbO2 , Pb grid material and acid – H2SO4  act as electrolyte.
One of the factors that limit the cycle life of the deep cycle battery  is corrosion process that is taking place between the positive grid material and the positive active. Corrosion leads to grid oxidation that support  the active positive material result in  grid ruin which it either  transmit or receive the current from or to grid and it will proceed continuously during float charge and shorten the lifetime of the deep cycle battery  and then leads to end of the service life to the situation that the current conductor (lead) is almost no longer available , (figure 1).
This phenomenon is also called premature capacity loss; this reaction not only decreases the positive grid conductivity but also consumes the water , and leads to the growth of the positive plates , the grid wires do not have the mechanical force due to the degree of corrosion. Corrosion lead to potential differences of the positive and the negative electrode, result in  self-discharge and faint performances of deep cycle battery .
Deep Cycle Battery  Corrosion Reasons
1- Continuous operation at high temperatures   particularly above 55C may reduce life as a result of an increase in the rate of  deep cycle battery’s corrosion
2- Excessive overcharging leads to increasing positive grid corrosion, and this is manifested as ‘‘growth’’ or expansion of the grid.
3-Moisture and dirt on top of and between cells permits stray intercell currents, resulting in corrosion through electrolysis.
4- Denser acid  tends to  form  at the bottom  of  the deep cycle battery.  especially  in  the  space  below  the  plates, this  can  cause  increased  corrosion.
5- The repeated charging and discharging of the deep cycle battery shortens the battery life through heat generation and corrosion.
Industrial  Esteems to Resist Deep Cycle Battery  Corrosion
1-Tubular plate types have a good corrosion resistance.
2- The pure lead provides a high corrosion resistance and an extremely long service life.
3- Use of pure or special alloy lead result in corrosion resistant increasing.
4- A light coating of petroleum jelly is used Intercell to prevent corrosion  .
Recommendations to Preserve A deep Cycle Battery    
1- Keeping the  deep cycle battery clean and dry, particularly top of the battery will minimize corrosion of cell post connectors and steel trays.  
2- Keep the batteries from rain water that could cause corrosion on the terminals of the batteries
3- A coating of no-oxide anti-corrosive grease on terminals will usually prevent corrosion.
4-A low charge current is desirable to minimize overcharge, grid corrosion associated with overcharge.
5-It is important to control the charge to maintain the morphology of the electrode, to prevent a rise in the temperature, particularly to a point where deleterious side reactions (corrosion) take place.
6- Overfilling must be avoided because the resultant overflow of acid electrolyte will cause tray corrosion, ground paths, and loss of cell capacity.