NOTE 3. For galvanic corrosion to happen , as we discussed earlier - we need a electrically conducting medium between the two dissimilar metals - may be water or acid or alkali or something which can conduct electricity. The above base material chart is prepared in taking sea water or 5% sodium chloride solution as conducting solution. Now if the dissimilar metals are kept in sodium hydroxide solution instead of sea water solution , the chart for base metal given above will change , so the position of weld metal in weld metal chart will also change.
It means for different medium we will have different chart for base metal and weld metal .