How To Fix Corroded Brake Pipes

When testing a vehicle, the mot tester often has to make decisions based on his experience and knowledge when there are no specific standards in the manual. One component without any written hard and fast rules regarding corrosion is the metal brake pipes. Nowadays most vehicle's brake pipes have an anti corrosion measure applied at the factory, in many cases the brake pipes are plastic coated, in general however the last inch or so doesn't have this coating. Also this plastic coating can crack at any bends in the pipework , leading to corrosion at these points. In such cases the only remedy is to replace the affected pipework .
The guidelines we're generally given refer pitting of the brake pipe such the pitting penetrates more than 1/3rd thickness of the brake pipe, not easy to visualise. Here are 2 examples of brake pipe corrosion, one an acceptable amount, one too badly corroded to be acceptable.

As can be seen in the example above the corrosion has penetrated far enough into the metal to cause it to expand and flake. When the above brake pipe was eased out of it's fixing clips to facilitate removal and replacement, it fractured at the bend approx 1 inch above the brake pipe union.
The example shown below whilst having corrosion on it's surface, the corrosion hasn't penetrated into the pipe itself to any degree. A quick rub down with wire wool and a coating of grease is likely to save this brake pipe for several more years before it needs replacing, assuming corrosion isn't more advanced further along some where in the rest of the pipe.

Unfortunately there are areas of the brake pipes in many cases not visible, they run above fuel tanks and above subframes and can be hidden by other underside items.