Mild-steel structures welded and then exposed to variable weather are at risk of hydrogen-induced or cold cracking. Moisture from the air or from a damp electrode coating releases hydrogen, which is absorbed into the weld.

Dissolved hydrogen collects in the weld and the heat-affected zone and, under the internal stresses of a restrained joint, initiates cracks, often some time after welding.

The way to guard against this is to limit the hydrogen entering the weld in the first place by choosing a low-hydrogen electrode, whose coating is formulated and kept dry so it adds very little hydrogen.

Keeping the hydrogen low prevents cold cracking and so protects the durability and integrity of the joint under changing conditions.

High current-carrying capacity (option 1) and fast deposition rate (option 3) only speed up the work; they do nothing to stop hydrogen cracking and can worsen quality if misused.

Higher tensile strength than the base metal (option 2) is not the aim; over-matching strength can raise hardness and actually increase, not reduce, the cracking risk, so it is not the critical factor here.

Controlling hydrogen is the decisive factor for weather-exposed mild steel.

Hence, the answer is Choosing an electrode with low hydrogen content to minimize cracking risk.