The rubber hose has nothing to do with breaking the emf for the metals in contact with water: Zinc-plated steel and Brass.

I suggest you to add a draw to allow a better understanding for other potential contributors.

Thank you Mr. Radu. Here is the picture of hose and fitting assembly.

I maintain the answer. The rubber is an isolator. The steel braid isn't involved in any electrochemical process. Zinc-plated steel and Brass may be involved in a local corrosion cell if both are in contact with the circulating liquid.

Thank you for your input Mr. Radu !

I agree with Mr. Radu. But I don't understand why you have selected the brass adapter if you have a concern with galvanic corrosion between the brass and zinc plated steel. Also, hose length effects on the galvanic corrosion potential has no influence on your problem because the problem is between two materials in intimate contact that are wetted by the fluid in the system - the hose is outside the volume of interest. The conductivity of the fluid will have an affect - lower conductivity should provide a lower corrosion rate than highly conductive fluids. PH is only one feature of a solution that can indicate relative conductivity of the fluid. Other elements/compounds dissolved in the fluid may determine the conductivity. If the zinc plated steel fitting was on one end of the hose and the brass fitting was on the other end of the hose, hose length would have a direct bearing on the resistance of the current loop - longer hose length would mean higher resistance, and presumably a lower corrosion rate. Depending on the fluid velocity in the system, you may also suffer from galvanic corrosion aided by the fluid stripping away the oxide layer on the material with the "softer" oxide layer, which reforms and gets stripped and so on. You could avoid all these concerns by using CPVC, or perhaps nylon, fittings which I am certain are available at your local hardware store.