Just as an aside, brake fluid has a built- in indicator of its condition; it starts out clear and gets progressively darker as it is contaminated with water. As a general rule of thumb, the fluid should be changed before it gets even remotely close to opaque. I change mine when it is 'tan' or similar. Brake fluid alone will not allow corrosion anywhere in the system that is flooded with brake fluid, any corrosion (usually around the seal lips of the slave cylinders) is due to collected water in the brake fluid.
Brian